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Limitations in Research – Types, Examples and Writing Guide

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Limitations in Research

Limitations in research refer to the factors that may affect the results, conclusions , and generalizability of a study. These limitations can arise from various sources, such as the design of the study, the sampling methods used, the measurement tools employed, and the limitations of the data analysis techniques.

Types of Limitations in Research

Types of Limitations in Research are as follows:

Sample Size Limitations

This refers to the size of the group of people or subjects that are being studied. If the sample size is too small, then the results may not be representative of the population being studied. This can lead to a lack of generalizability of the results.

Time Limitations

Time limitations can be a constraint on the research process . This could mean that the study is unable to be conducted for a long enough period of time to observe the long-term effects of an intervention, or to collect enough data to draw accurate conclusions.

Selection Bias

This refers to a type of bias that can occur when the selection of participants in a study is not random. This can lead to a biased sample that is not representative of the population being studied.

Confounding Variables

Confounding variables are factors that can influence the outcome of a study, but are not being measured or controlled for. These can lead to inaccurate conclusions or a lack of clarity in the results.

Measurement Error

This refers to inaccuracies in the measurement of variables, such as using a faulty instrument or scale. This can lead to inaccurate results or a lack of validity in the study.

Ethical Limitations

Ethical limitations refer to the ethical constraints placed on research studies. For example, certain studies may not be allowed to be conducted due to ethical concerns, such as studies that involve harm to participants.

Examples of Limitations in Research

Some Examples of Limitations in Research are as follows:

Research Title: “The Effectiveness of Machine Learning Algorithms in Predicting Customer Behavior”

Limitations:

• The study only considered a limited number of machine learning algorithms and did not explore the effectiveness of other algorithms.
• The study used a specific dataset, which may not be representative of all customer behaviors or demographics.
• The study did not consider the potential ethical implications of using machine learning algorithms in predicting customer behavior.

Research Title: “The Impact of Online Learning on Student Performance in Computer Science Courses”

• The study was conducted during the COVID-19 pandemic, which may have affected the results due to the unique circumstances of remote learning.
• The study only included students from a single university, which may limit the generalizability of the findings to other institutions.
• The study did not consider the impact of individual differences, such as prior knowledge or motivation, on student performance in online learning environments.

Research Title: “The Effect of Gamification on User Engagement in Mobile Health Applications”

• The study only tested a specific gamification strategy and did not explore the effectiveness of other gamification techniques.
• The study relied on self-reported measures of user engagement, which may be subject to social desirability bias or measurement errors.
• The study only included a specific demographic group (e.g., young adults) and may not be generalizable to other populations with different preferences or needs.

How to Write Limitations in Research

When writing about the limitations of a research study, it is important to be honest and clear about the potential weaknesses of your work. Here are some tips for writing about limitations in research:

• Identify the limitations: Start by identifying the potential limitations of your research. These may include sample size, selection bias, measurement error, or other issues that could affect the validity and reliability of your findings.
• Be honest and objective: When describing the limitations of your research, be honest and objective. Do not try to minimize or downplay the limitations, but also do not exaggerate them. Be clear and concise in your description of the limitations.
• Provide context: It is important to provide context for the limitations of your research. For example, if your sample size was small, explain why this was the case and how it may have affected your results. Providing context can help readers understand the limitations in a broader context.
• Discuss implications : Discuss the implications of the limitations for your research findings. For example, if there was a selection bias in your sample, explain how this may have affected the generalizability of your findings. This can help readers understand the limitations in terms of their impact on the overall validity of your research.
• Provide suggestions for future research : Finally, provide suggestions for future research that can address the limitations of your study. This can help readers understand how your research fits into the broader field and can provide a roadmap for future studies.

Purpose of Limitations in Research

There are several purposes of limitations in research. Here are some of the most important ones:

• To acknowledge the boundaries of the study : Limitations help to define the scope of the research project and set realistic expectations for the findings. They can help to clarify what the study is not intended to address.
• To identify potential sources of bias: Limitations can help researchers identify potential sources of bias in their research design, data collection, or analysis. This can help to improve the validity and reliability of the findings.
• To provide opportunities for future research: Limitations can highlight areas for future research and suggest avenues for further exploration. This can help to advance knowledge in a particular field.
• To demonstrate transparency and accountability: By acknowledging the limitations of their research, researchers can demonstrate transparency and accountability to their readers, peers, and funders. This can help to build trust and credibility in the research community.
• To encourage critical thinking: Limitations can encourage readers to critically evaluate the study’s findings and consider alternative explanations or interpretations. This can help to promote a more nuanced and sophisticated understanding of the topic under investigation.

When to Write Limitations in Research

Limitations should be included in research when they help to provide a more complete understanding of the study’s results and implications. A limitation is any factor that could potentially impact the accuracy, reliability, or generalizability of the study’s findings.

It is important to identify and discuss limitations in research because doing so helps to ensure that the results are interpreted appropriately and that any conclusions drawn are supported by the available evidence. Limitations can also suggest areas for future research, highlight potential biases or confounding factors that may have affected the results, and provide context for the study’s findings.

Generally, limitations should be discussed in the conclusion section of a research paper or thesis, although they may also be mentioned in other sections, such as the introduction or methods. The specific limitations that are discussed will depend on the nature of the study, the research question being investigated, and the data that was collected.

Examples of limitations that might be discussed in research include sample size limitations, data collection methods, the validity and reliability of measures used, and potential biases or confounding factors that could have affected the results. It is important to note that limitations should not be used as a justification for poor research design or methodology, but rather as a way to enhance the understanding and interpretation of the study’s findings.

Importance of Limitations in Research

Here are some reasons why limitations are important in research:

• Enhances the credibility of research: Limitations highlight the potential weaknesses and threats to validity, which helps readers to understand the scope and boundaries of the study. This improves the credibility of research by acknowledging its limitations and providing a clear picture of what can and cannot be concluded from the study.
• Facilitates replication: By highlighting the limitations, researchers can provide detailed information about the study’s methodology, data collection, and analysis. This information helps other researchers to replicate the study and test the validity of the findings, which enhances the reliability of research.
• Guides future research : Limitations provide insights into areas for future research by identifying gaps or areas that require further investigation. This can help researchers to design more comprehensive and effective studies that build on existing knowledge.
• Provides a balanced view: Limitations help to provide a balanced view of the research by highlighting both strengths and weaknesses. This ensures that readers have a clear understanding of the study’s limitations and can make informed decisions about the generalizability and applicability of the findings.

Advantages of Limitations in Research

Here are some potential advantages of limitations in research:

• Focus : Limitations can help researchers focus their study on a specific area or population, which can make the research more relevant and useful.
• Realism : Limitations can make a study more realistic by reflecting the practical constraints and challenges of conducting research in the real world.
• Innovation : Limitations can spur researchers to be more innovative and creative in their research design and methodology, as they search for ways to work around the limitations.
• Rigor : Limitations can actually increase the rigor and credibility of a study, as researchers are forced to carefully consider the potential sources of bias and error, and address them to the best of their abilities.
• Generalizability : Limitations can actually improve the generalizability of a study by ensuring that it is not overly focused on a specific sample or situation, and that the results can be applied more broadly.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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How to Write Limitations of the Study (with examples)

This blog emphasizes the importance of recognizing and effectively writing about limitations in research. It discusses the types of limitations, their significance, and provides guidelines for writing about them, highlighting their role in advancing scholarly research.

Updated on August 24, 2023

No matter how well thought out, every research endeavor encounters challenges. There is simply no way to predict all possible variances throughout the process.

These uncharted boundaries and abrupt constraints are known as limitations in research . Identifying and acknowledging limitations is crucial for conducting rigorous studies. Limitations provide context and shed light on gaps in the prevailing inquiry and literature.

This article explores the importance of recognizing limitations and discusses how to write them effectively. By interpreting limitations in research and considering prevalent examples, we aim to reframe the perception from shameful mistakes to respectable revelations.

What are limitations in research?

In the clearest terms, research limitations are the practical or theoretical shortcomings of a study that are often outside of the researcher’s control . While these weaknesses limit the generalizability of a study’s conclusions, they also present a foundation for future research.

Sometimes limitations arise from tangible circumstances like time and funding constraints, or equipment and participant availability. Other times the rationale is more obscure and buried within the research design. Common types of limitations and their ramifications include:

• Theoretical: limits the scope, depth, or applicability of a study.
• Methodological: limits the quality, quantity, or diversity of the data.
• Empirical: limits the representativeness, validity, or reliability of the data.
• Analytical: limits the accuracy, completeness, or significance of the findings.
• Ethical: limits the access, consent, or confidentiality of the data.

Regardless of how, when, or why they arise, limitations are a natural part of the research process and should never be ignored . Like all other aspects, they are vital in their own purpose.

Why is identifying limitations important?

Whether to seek acceptance or avoid struggle, humans often instinctively hide flaws and mistakes. Merging this thought process into research by attempting to hide limitations, however, is a bad idea. It has the potential to negate the validity of outcomes and damage the reputation of scholars.

By identifying and addressing limitations throughout a project, researchers strengthen their arguments and curtail the chance of peer censure based on overlooked mistakes. Pointing out these flaws shows an understanding of variable limits and a scrupulous research process.

Showing awareness of and taking responsibility for a project’s boundaries and challenges validates the integrity and transparency of a researcher. It further demonstrates the researchers understand the applicable literature and have thoroughly evaluated their chosen research methods.

Presenting limitations also benefits the readers by providing context for research findings. It guides them to interpret the project’s conclusions only within the scope of very specific conditions. By allowing for an appropriate generalization of the findings that is accurately confined by research boundaries and is not too broad, limitations boost a study’s credibility .

Limitations are true assets to the research process. They highlight opportunities for future research. When researchers identify the limitations of their particular approach to a study question, they enable precise transferability and improve chances for reproducibility. 

Simply stating a project’s limitations is not adequate for spurring further research, though. To spark the interest of other researchers, these acknowledgements must come with thorough explanations regarding how the limitations affected the current study and how they can potentially be overcome with amended methods.

How to write limitations

Typically, the information about a study’s limitations is situated either at the beginning of the discussion section to provide context for readers or at the conclusion of the discussion section to acknowledge the need for further research. However, it varies depending upon the target journal or publication guidelines. 

Don’t hide your limitations

It is also important to not bury a limitation in the body of the paper unless it has a unique connection to a topic in that section. If so, it needs to be reiterated with the other limitations or at the conclusion of the discussion section. Wherever it is included in the manuscript, ensure that the limitations section is prominently positioned and clearly introduced.

While maintaining transparency by disclosing limitations means taking a comprehensive approach, it is not necessary to discuss everything that could have potentially gone wrong during the research study. If there is no commitment to investigation in the introduction, it is unnecessary to consider the issue a limitation to the research. Wholly consider the term ‘limitations’ and ask, “Did it significantly change or limit the possible outcomes?” Then, qualify the occurrence as either a limitation to include in the current manuscript or as an idea to note for other projects. 

Writing limitations

Once the limitations are concretely identified and it is decided where they will be included in the paper, researchers are ready for the writing task. Including only what is pertinent, keeping explanations detailed but concise, and employing the following guidelines is key for crafting valuable limitations:

1) Identify and describe the limitations : Clearly introduce the limitation by classifying its form and specifying its origin. For example:

• An unintentional bias encountered during data collection
• An intentional use of unplanned post-hoc data analysis

2) Explain the implications : Describe how the limitation potentially influences the study’s findings and how the validity and generalizability are subsequently impacted. Provide examples and evidence to support claims of the limitations’ effects without making excuses or exaggerating their impact. Overall, be transparent and objective in presenting the limitations, without undermining the significance of the research. 

3) Provide alternative approaches for future studies : Offer specific suggestions for potential improvements or avenues for further investigation. Demonstrate a proactive approach by encouraging future research that addresses the identified gaps and, therefore, expands the knowledge base.

Whether presenting limitations as an individual section within the manuscript or as a subtopic in the discussion area, authors should use clear headings and straightforward language to facilitate readability. There is no need to complicate limitations with jargon, computations, or complex datasets.

Examples of common limitations

Limitations are generally grouped into two categories , methodology and research process .

Methodology limitations

Methodology may include limitations due to:

• Sample size
• Lack of available or reliable data
• Lack of prior research studies on the topic
• Measure used to collect the data
• Self-reported data

The researcher is addressing how the large sample size requires a reassessment of the measures used to collect and analyze the data.

Research process limitations

Limitations during the research process may arise from:

• Access to information
• Longitudinal effects
• Cultural and other biases
• Language fluency
• Time constraints

The author is pointing out that the model’s estimates are based on potentially biased observational studies.

Final thoughts

Successfully proving theories and touting great achievements are only two very narrow goals of scholarly research. The true passion and greatest efforts of researchers comes more in the form of confronting assumptions and exploring the obscure.

In many ways, recognizing and sharing the limitations of a research study both allows for and encourages this type of discovery that continuously pushes research forward. By using limitations to provide a transparent account of the project's boundaries and to contextualize the findings, researchers pave the way for even more robust and impactful research in the future.

Charla Viera, MS

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The limitations of the study are those characteristics of design or methodology that impacted or influenced the interpretation of the findings from your research. Study limitations are the constraints placed on the ability to generalize from the results, to further describe applications to practice, and/or related to the utility of findings that are the result of the ways in which you initially chose to design the study or the method used to establish internal and external validity or the result of unanticipated challenges that emerged during the study.

Price, James H. and Judy Murnan. “Research Limitations and the Necessity of Reporting Them.” American Journal of Health Education 35 (2004): 66-67; Theofanidis, Dimitrios and Antigoni Fountouki. "Limitations and Delimitations in the Research Process." Perioperative Nursing 7 (September-December 2018): 155-163. .

Importance of...

Always acknowledge a study's limitations. It is far better that you identify and acknowledge your study’s limitations than to have them pointed out by your professor and have your grade lowered because you appeared to have ignored them or didn't realize they existed.

Keep in mind that acknowledgment of a study's limitations is an opportunity to make suggestions for further research. If you do connect your study's limitations to suggestions for further research, be sure to explain the ways in which these unanswered questions may become more focused because of your study.

Acknowledgment of a study's limitations also provides you with opportunities to demonstrate that you have thought critically about the research problem, understood the relevant literature published about it, and correctly assessed the methods chosen for studying the problem. A key objective of the research process is not only discovering new knowledge but also to confront assumptions and explore what we don't know.

Claiming limitations is a subjective process because you must evaluate the impact of those limitations . Don't just list key weaknesses and the magnitude of a study's limitations. To do so diminishes the validity of your research because it leaves the reader wondering whether, or in what ways, limitation(s) in your study may have impacted the results and conclusions. Limitations require a critical, overall appraisal and interpretation of their impact. You should answer the question: do these problems with errors, methods, validity, etc. eventually matter and, if so, to what extent?

Price, James H. and Judy Murnan. “Research Limitations and the Necessity of Reporting Them.” American Journal of Health Education 35 (2004): 66-67; Structure: How to Structure the Research Limitations Section of Your Dissertation. Dissertations and Theses: An Online Textbook. Laerd.com.

Descriptions of Possible Limitations

All studies have limitations . However, it is important that you restrict your discussion to limitations related to the research problem under investigation. For example, if a meta-analysis of existing literature is not a stated purpose of your research, it should not be discussed as a limitation. Do not apologize for not addressing issues that you did not promise to investigate in the introduction of your paper.

Here are examples of limitations related to methodology and the research process you may need to describe and discuss how they possibly impacted your results. Note that descriptions of limitations should be stated in the past tense because they were discovered after you completed your research.

Possible Methodological Limitations

• Sample size -- the number of the units of analysis you use in your study is dictated by the type of research problem you are investigating. Note that, if your sample size is too small, it will be difficult to find significant relationships from the data, as statistical tests normally require a larger sample size to ensure a representative distribution of the population and to be considered representative of groups of people to whom results will be generalized or transferred. Note that sample size is generally less relevant in qualitative research if explained in the context of the research problem.
• Lack of available and/or reliable data -- a lack of data or of reliable data will likely require you to limit the scope of your analysis, the size of your sample, or it can be a significant obstacle in finding a trend and a meaningful relationship. You need to not only describe these limitations but provide cogent reasons why you believe data is missing or is unreliable. However, don’t just throw up your hands in frustration; use this as an opportunity to describe a need for future research based on designing a different method for gathering data.
• Lack of prior research studies on the topic -- citing prior research studies forms the basis of your literature review and helps lay a foundation for understanding the research problem you are investigating. Depending on the currency or scope of your research topic, there may be little, if any, prior research on your topic. Before assuming this to be true, though, consult with a librarian! In cases when a librarian has confirmed that there is little or no prior research, you may be required to develop an entirely new research typology [for example, using an exploratory rather than an explanatory research design ]. Note again that discovering a limitation can serve as an important opportunity to identify new gaps in the literature and to describe the need for further research.
• Measure used to collect the data -- sometimes it is the case that, after completing your interpretation of the findings, you discover that the way in which you gathered data inhibited your ability to conduct a thorough analysis of the results. For example, you regret not including a specific question in a survey that, in retrospect, could have helped address a particular issue that emerged later in the study. Acknowledge the deficiency by stating a need for future researchers to revise the specific method for gathering data.
• Self-reported data -- whether you are relying on pre-existing data or you are conducting a qualitative research study and gathering the data yourself, self-reported data is limited by the fact that it rarely can be independently verified. In other words, you have to the accuracy of what people say, whether in interviews, focus groups, or on questionnaires, at face value. However, self-reported data can contain several potential sources of bias that you should be alert to and note as limitations. These biases become apparent if they are incongruent with data from other sources. These are: (1) selective memory [remembering or not remembering experiences or events that occurred at some point in the past]; (2) telescoping [recalling events that occurred at one time as if they occurred at another time]; (3) attribution [the act of attributing positive events and outcomes to one's own agency, but attributing negative events and outcomes to external forces]; and, (4) exaggeration [the act of representing outcomes or embellishing events as more significant than is actually suggested from other data].

Possible Limitations of the Researcher

• Access -- if your study depends on having access to people, organizations, data, or documents and, for whatever reason, access is denied or limited in some way, the reasons for this needs to be described. Also, include an explanation why being denied or limited access did not prevent you from following through on your study.
• Longitudinal effects -- unlike your professor, who can literally devote years [even a lifetime] to studying a single topic, the time available to investigate a research problem and to measure change or stability over time is constrained by the due date of your assignment. Be sure to choose a research problem that does not require an excessive amount of time to complete the literature review, apply the methodology, and gather and interpret the results. If you're unsure whether you can complete your research within the confines of the assignment's due date, talk to your professor.
• Cultural and other type of bias -- we all have biases, whether we are conscience of them or not. Bias is when a person, place, event, or thing is viewed or shown in a consistently inaccurate way. Bias is usually negative, though one can have a positive bias as well, especially if that bias reflects your reliance on research that only support your hypothesis. When proof-reading your paper, be especially critical in reviewing how you have stated a problem, selected the data to be studied, what may have been omitted, the manner in which you have ordered events, people, or places, how you have chosen to represent a person, place, or thing, to name a phenomenon, or to use possible words with a positive or negative connotation. NOTE :   If you detect bias in prior research, it must be acknowledged and you should explain what measures were taken to avoid perpetuating that bias. For example, if a previous study only used boys to examine how music education supports effective math skills, describe how your research expands the study to include girls.
• Fluency in a language -- if your research focuses , for example, on measuring the perceived value of after-school tutoring among Mexican-American ESL [English as a Second Language] students and you are not fluent in Spanish, you are limited in being able to read and interpret Spanish language research studies on the topic or to speak with these students in their primary language. This deficiency should be acknowledged.

Aguinis, Hermam and Jeffrey R. Edwards. “Methodological Wishes for the Next Decade and How to Make Wishes Come True.” Journal of Management Studies 51 (January 2014): 143-174; Brutus, Stéphane et al. "Self-Reported Limitations and Future Directions in Scholarly Reports: Analysis and Recommendations." Journal of Management 39 (January 2013): 48-75; Senunyeme, Emmanuel K. Business Research Methods. Powerpoint Presentation. Regent University of Science and Technology; ter Riet, Gerben et al. “All That Glitters Isn't Gold: A Survey on Acknowledgment of Limitations in Biomedical Studies.” PLOS One 8 (November 2013): 1-6.

Structure and Writing Style

Information about the limitations of your study are generally placed either at the beginning of the discussion section of your paper so the reader knows and understands the limitations before reading the rest of your analysis of the findings, or, the limitations are outlined at the conclusion of the discussion section as an acknowledgement of the need for further study. Statements about a study's limitations should not be buried in the body [middle] of the discussion section unless a limitation is specific to something covered in that part of the paper. If this is the case, though, the limitation should be reiterated at the conclusion of the section.

If you determine that your study is seriously flawed due to important limitations , such as, an inability to acquire critical data, consider reframing it as an exploratory study intended to lay the groundwork for a more complete research study in the future. Be sure, though, to specifically explain the ways that these flaws can be successfully overcome in a new study.

But, do not use this as an excuse for not developing a thorough research paper! Review the tab in this guide for developing a research topic . If serious limitations exist, it generally indicates a likelihood that your research problem is too narrowly defined or that the issue or event under study is too recent and, thus, very little research has been written about it. If serious limitations do emerge, consult with your professor about possible ways to overcome them or how to revise your study.

When discussing the limitations of your research, be sure to:

• Describe each limitation in detailed but concise terms;
• Explain why each limitation exists;
• Provide the reasons why each limitation could not be overcome using the method(s) chosen to acquire or gather the data [cite to other studies that had similar problems when possible];
• Assess the impact of each limitation in relation to the overall findings and conclusions of your study; and,
• If appropriate, describe how these limitations could point to the need for further research.

Remember that the method you chose may be the source of a significant limitation that has emerged during your interpretation of the results [for example, you didn't interview a group of people that you later wish you had]. If this is the case, don't panic. Acknowledge it, and explain how applying a different or more robust methodology might address the research problem more effectively in a future study. A underlying goal of scholarly research is not only to show what works, but to demonstrate what doesn't work or what needs further clarification.

Aguinis, Hermam and Jeffrey R. Edwards. “Methodological Wishes for the Next Decade and How to Make Wishes Come True.” Journal of Management Studies 51 (January 2014): 143-174; Brutus, Stéphane et al. "Self-Reported Limitations and Future Directions in Scholarly Reports: Analysis and Recommendations." Journal of Management 39 (January 2013): 48-75; Ioannidis, John P.A. "Limitations are not Properly Acknowledged in the Scientific Literature." Journal of Clinical Epidemiology 60 (2007): 324-329; Pasek, Josh. Writing the Empirical Social Science Research Paper: A Guide for the Perplexed. January 24, 2012. Academia.edu; Structure: How to Structure the Research Limitations Section of Your Dissertation. Dissertations and Theses: An Online Textbook. Laerd.com; What Is an Academic Paper? Institute for Writing Rhetoric. Dartmouth College; Writing the Experimental Report: Methods, Results, and Discussion. The Writing Lab and The OWL. Purdue University.

Writing Tip

Don't Inflate the Importance of Your Findings!

After all the hard work and long hours devoted to writing your research paper, it is easy to get carried away with attributing unwarranted importance to what you’ve done. We all want our academic work to be viewed as excellent and worthy of a good grade, but it is important that you understand and openly acknowledge the limitations of your study. Inflating the importance of your study's findings could be perceived by your readers as an attempt hide its flaws or encourage a biased interpretation of the results. A small measure of humility goes a long way!

Another Writing Tip

Negative Results are Not a Limitation!

Negative evidence refers to findings that unexpectedly challenge rather than support your hypothesis. If you didn't get the results you anticipated, it may mean your hypothesis was incorrect and needs to be reformulated. Or, perhaps you have stumbled onto something unexpected that warrants further study. Moreover, the absence of an effect may be very telling in many situations, particularly in experimental research designs. In any case, your results may very well be of importance to others even though they did not support your hypothesis. Do not fall into the trap of thinking that results contrary to what you expected is a limitation to your study. If you carried out the research well, they are simply your results and only require additional interpretation.

Lewis, George H. and Jonathan F. Lewis. “The Dog in the Night-Time: Negative Evidence in Social Research.” The British Journal of Sociology 31 (December 1980): 544-558.

Yet Another Writing Tip

Sample Size Limitations in Qualitative Research

Sample sizes are typically smaller in qualitative research because, as the study goes on, acquiring more data does not necessarily lead to more information. This is because one occurrence of a piece of data, or a code, is all that is necessary to ensure that it becomes part of the analysis framework. However, it remains true that sample sizes that are too small cannot adequately support claims of having achieved valid conclusions and sample sizes that are too large do not permit the deep, naturalistic, and inductive analysis that defines qualitative inquiry. Determining adequate sample size in qualitative research is ultimately a matter of judgment and experience in evaluating the quality of the information collected against the uses to which it will be applied and the particular research method and purposeful sampling strategy employed. If the sample size is found to be a limitation, it may reflect your judgment about the methodological technique chosen [e.g., single life history study versus focus group interviews] rather than the number of respondents used.

Boddy, Clive Roland. "Sample Size for Qualitative Research." Qualitative Market Research: An International Journal 19 (2016): 426-432; Huberman, A. Michael and Matthew B. Miles. "Data Management and Analysis Methods." In Handbook of Qualitative Research . Norman K. Denzin and Yvonna S. Lincoln, eds. (Thousand Oaks, CA: Sage, 1994), pp. 428-444; Blaikie, Norman. "Confounding Issues Related to Determining Sample Size in Qualitative Research." International Journal of Social Research Methodology 21 (2018): 635-641; Oppong, Steward Harrison. "The Problem of Sampling in qualitative Research." Asian Journal of Management Sciences and Education 2 (2013): 202-210.

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What are the limitations in research and how to write them?

Learn about the potential limitations in research and how to appropriately address them in order to deliver honest and ethical research.

It is fairly uncommon for researchers to stumble into the term research limitations when working on their research paper. Limitations in research can arise owing to constraints on design, methods, materials, and so on, and these aspects, unfortunately, may have an influence on your subject’s findings.

In this Mind The Graph’s article, we’ll discuss some recommendations for writing limitations in research , provide examples of various common types of limitations, and suggest how to properly present this information.

What are the limitations in research?

The limitations in research are the constraints in design, methods or even researchers’ limitations that affect and influence the interpretation of your research’s ultimate findings. These are limitations on the generalization and usability of findings that emerge from the design of the research and/or the method employed to ensure validity both internally and externally. 

Researchers are usually cautious to acknowledge the limitations of their research in their publications for fear of undermining the research’s scientific validity. No research is faultless or covers every possible angle. As a result, addressing the constraints of your research exhibits honesty and integrity .

Why should include limitations of research in my paper?

Though limitations tackle potential flaws in research, commenting on them at the conclusion of your paper, by demonstrating that you are aware of these limitations and explaining how they impact the conclusions that may be taken from the research, improves your research by disclosing any issues before other researchers or reviewers do . 

Additionally, emphasizing research constraints implies that you have thoroughly investigated the ramifications of research shortcomings and have a thorough understanding of your research problem. 

Limits exist in any research; being honest about them and explaining them would impress researchers and reviewers more than disregarding them. 

Remember that acknowledging a research’s shortcomings offers a chance to provide ideas for future research, but be careful to describe how your study may help to concentrate on these outstanding problems.

Possible limitations examples

Here are some limitations connected to methodology and the research procedure that you may need to explain and discuss in connection to your findings.

Methodological limitations

Sample size.

The number of units of analysis used in your study is determined by the sort of research issue being investigated. It is important to note that if your sample is too small, finding significant connections in the data will be challenging, as statistical tests typically require a larger sample size to ensure a fair representation and this can be limiting. 

Lack of available or reliable data

A lack of data or trustworthy data will almost certainly necessitate limiting the scope of your research or the size of your sample, or it can be a substantial impediment to identifying a pattern and a relevant connection.

Lack of prior research on the subject

Citing previous research papers forms the basis of your literature review and aids in comprehending the research subject you are researching. Yet there may be little if any, past research on your issue.

The measure used to collect data

After finishing your analysis of the findings, you realize that the method you used to collect data limited your capacity to undertake a comprehensive evaluation of the findings. Recognize the flaw by mentioning that future researchers should change the specific approach for data collection.

Issues with research samples and selection

Sampling inaccuracies arise when a probability sampling method is employed to choose a sample, but that sample does not accurately represent the overall population or the relevant group. As a result, your study suffers from “sampling bias” or “selection bias.”

Limitations of the research

When your research requires polling certain persons or a specific group, you may have encountered the issue of limited access to these interviewees. Because of the limited access, you may need to reorganize or rearrange your research. In this scenario, explain why access is restricted and ensure that your findings are still trustworthy and valid despite the constraint.

Time constraints

Practical difficulties may limit the amount of time available to explore a research issue and monitor changes as they occur. If time restrictions have any detrimental influence on your research, recognize this impact by expressing the necessity for a future investigation.

Due to their cultural origins or opinions on observed events, researchers may carry biased opinions, which can influence the credibility of a research. Furthermore, researchers may exhibit biases toward data and conclusions that only support their hypotheses or arguments.

The structure of the limitations section 

The limitations of your research are usually stated at the beginning of the discussion section of your paper so that the reader is aware of and comprehends the limitations prior to actually reading the rest of your findings, or they are stated at the end of the discussion section as an acknowledgment of the need for further research.

The ideal way is to divide your limitations section into three steps: 

1. Identify the research constraints; 

2. Describe in great detail how they affect your research; 

3. Mention the opportunity for future investigations and give possibilities. 

By following this method while addressing the constraints of your research, you will be able to effectively highlight your research’s shortcomings without jeopardizing the quality and integrity of your research.

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How to present limitations in research

Last updated

30 January 2024

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Limitations don’t invalidate or diminish your results, but it’s best to acknowledge them. This will enable you to address any questions your study failed to answer because of them.

In this guide, learn how to recognize, present, and overcome limitations in research.

• What is a research limitation?

Research limitations are weaknesses in your research design or execution that may have impacted outcomes and conclusions. Uncovering limitations doesn’t necessarily indicate poor research design—it just means you encountered challenges you couldn’t have anticipated that limited your research efforts.

Does basic research have limitations?

Basic research aims to provide more information about your research topic . It requires the same standard research methodology and data collection efforts as any other research type, and it can also have limitations.

• Common research limitations

Researchers encounter common limitations when embarking on a study. Limitations can occur in relation to the methods you apply or the research process you design. They could also be connected to you as the researcher.

Methodology limitations

Not having access to data or reliable information can impact the methods used to facilitate your research. A lack of data or reliability may limit the parameters of your study area and the extent of your exploration.

Your sample size may also be affected because you won’t have any direction on how big or small it should be and who or what you should include. Having too few participants won’t adequately represent the population or groups of people needed to draw meaningful conclusions.

Research process limitations

The study’s design can impose constraints on the process. For example, as you’re conducting the research, issues may arise that don’t conform to the data collection methodology you developed. You may not realize until well into the process that you should have incorporated more specific questions or comprehensive experiments to generate the data you need to have confidence in your results.

Constraints on resources can also have an impact. Being limited on participants or participation incentives may limit your sample sizes. Insufficient tools, equipment, and materials to conduct a thorough study may also be a factor.

Common researcher limitations

Here are some of the common researcher limitations you may encounter:

Time: some research areas require multi-year longitudinal approaches, but you might not be able to dedicate that much time. Imagine you want to measure how much memory a person loses as they age. This may involve conducting multiple tests on a sample of participants over 20–30 years, which may be impossible.

Bias: researchers can consciously or unconsciously apply bias to their research. Biases can contribute to relying on research sources and methodologies that will only support your beliefs about the research you’re embarking on. You might also omit relevant issues or participants from the scope of your study because of your biases.

Limited access to data : you may need to pay to access specific databases or journals that would be helpful to your research process. You might also need to gain information from certain people or organizations but have limited access to them. These cases require readjusting your process and explaining why your findings are still reliable.

• Why is it important to identify limitations?

Identifying limitations adds credibility to research and provides a deeper understanding of how you arrived at your conclusions.

Constraints may have prevented you from collecting specific data or information you hoped would prove or disprove your hypothesis or provide a more comprehensive understanding of your research topic.

However, identifying the limitations contributing to your conclusions can inspire further research efforts that help gather more substantial information and data.

• Where to put limitations in a research paper

A research paper is broken up into different sections that appear in the following order:

Introduction

Methodology

The discussion portion of your paper explores your findings and puts them in the context of the overall research. Either place research limitations at the beginning of the discussion section before the analysis of your findings or at the end of the section to indicate that further research needs to be pursued.

What not to include in the limitations section

Evidence that doesn’t support your hypothesis is not a limitation, so you shouldn’t include it in the limitation section. Don’t just list limitations and their degree of severity without further explanation.

• How to present limitations

You’ll want to present the limitations of your study in a way that doesn’t diminish the validity of your research and leave the reader wondering if your results and conclusions have been compromised.

Include only the limitations that directly relate to and impact how you addressed your research questions. Following a specific format enables the reader to develop an understanding of the weaknesses within the context of your findings without doubting the quality and integrity of your research.

Identify the limitations specific to your study

You don’t have to identify every possible limitation that might have occurred during your research process. Only identify those that may have influenced the quality of your findings and your ability to answer your research question.

Explain study limitations in detail

This explanation should be the most significant portion of your limitation section.

Link each limitation with an interpretation and appraisal of their impact on the study. You’ll have to evaluate and explain whether the error, method, or validity issues influenced the study’s outcome and how.

Propose a direction for future studies and present alternatives

In this section, suggest how researchers can avoid the pitfalls you experienced during your research process.

If an issue with methodology was a limitation, propose alternate methods that may help with a smoother and more conclusive research project . Discuss the pros and cons of your alternate recommendation.

Describe steps taken to minimize each limitation

You probably took steps to try to address or mitigate limitations when you noticed them throughout the course of your research project. Describe these steps in the limitation section.

• Limitation example

“Approaches like stem cell transplantation and vaccination in AD [Alzheimer’s disease] work on a cellular or molecular level in the laboratory. However, translation into clinical settings will remain a challenge for the next decade.”

The authors are saying that even though these methods showed promise in helping people with memory loss when conducted in the lab (in other words, using animal studies), more studies are needed. These may be controlled clinical trials, for example. 

However, the short life span of stem cells outside the lab and the vaccination’s severe inflammatory side effects are limitations. Researchers won’t be able to conduct clinical trials until these issues are overcome.

• How to overcome limitations in research

You’ve already started on the road to overcoming limitations in research by acknowledging that they exist. However, you need to ensure readers don’t mistake weaknesses for errors within your research design.

To do this, you’ll need to justify and explain your rationale for the methods, research design, and analysis tools you chose and how you noticed they may have presented limitations.

Your readers need to know that even when limitations presented themselves, you followed best practices and the ethical standards of your field. You didn’t violate any rules and regulations during your research process.

You’ll also want to reinforce the validity of your conclusions and results with multiple sources, methods, and perspectives. This prevents readers from assuming your findings were derived from a single or biased source.

• Learning and improving starts with limitations in research

Dealing with limitations with transparency and integrity helps identify areas for future improvements and developments. It’s a learning process, providing valuable insights into how you can improve methodologies, expand sample sizes, or explore alternate approaches to further support the validity of your findings.

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Limitations in Medical Research: Recognition, Influence, and Warning

Douglas e ott , md, mba.

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Address correspondence to: Douglas E. Ott, MD, MBA, 109 Preston Court, Macon, GA 31210, USA, Telephone: 478-747-1655, E-mail: [email protected] .

Corresponding author.

Background:

As the number of limitations increases in a medical research article, their consequences multiply and the validity of findings decreases. How often do limitations occur in a medical article? What are the implications of limitation interaction? How often are the conclusions hedged in their explanation?

To identify the number, type, and frequency of limitations and words used to describe conclusion(s) in medical research articles.

Search, analysis, and evaluation of open access research articles from 2021 and 2022 from the Journal of the Society of Laparoscopic and Robotic Surgery and 2022 Surgical Endoscopy for type(s) of limitation(s) admitted to by author(s) and the number of times they occurred. Limitations not admitted to were found, obvious, and not claimed. An automated text analysis was performed for hedging words in conclusion statements. A limitation index score is proposed to gauge the validity of statements and conclusions as the number of limitations increases.

A total of 298 articles were reviewed and analyzed, finding 1,764 limitations. Four articles had no limitations. The average was between 3.7% and 6.9% per article. Hedging, weasel words and words of estimative probability description was found in 95.6% of the conclusions.

Conclusions:

Limitations and their number matter. The greater the number of limitations and ramifications of their effects, the more outcomes and conclusions are affected. Wording ambiguity using hedging or weasel words shows that limitations affect the uncertainty of claims. The limitation index scoring method shows the diminished validity of finding(s) and conclusion(s).

Keywords: Bias, Hedging, Limitations, Methods, Research, Uncertainty, Validity

INTRODUCTION

As the number of limitations in a medical research article increases, does their influence have a more significant effect than each one considered separately, making the findings and conclusions less reliable and valid? Limitations are known variables that influence data collection and findings and compromise outcomes, conclusions, and inferences. A large body of work recognizes the effect(s) and consequence(s) of limitations. 1 – 77 Other than the ones known to the author(s), unknown and unrecognized limitations influence research credibility. This study and analysis aim to determine how frequently and what limitations are found in peer-reviewed open-access medical articles for laparoscopic/endoscopic surgeons.

This research is about limitations, how often they occur and explained and/or justified. Failure to disclose limitations in medical writing limits proper decision-making and understanding of the material presented. All articles have limitations and constraints. Not acknowledging limitations is a lack of candor, ignorance, or a deliberate omission. To reduce the suspicion of invalid conclusions limitations and their effects must be acknowledged and explained. This allows for a clearer more focused assessment of the article’s subject matter without explaining its findings and conclusions using hedging and words of estimative probability. 78 , 79

An evaluation of open access research/meta-analysis/case series/methodologies/review articles published in the Journal of the Society of Laparoendoscopic and Robotic Surgery ( JSLS ) for 2021 and 2022 (129) and commentary/guidelines/new technology/practice guidelines/review/SAGES Masters Program articles in Surgical Endoscopy ( Surg Endosc ) for 2022 (169) totaling 298 were read and evaluated by automated text analysis for limitations admitted to by the paper’s authors using such words as “limitations,” “limits,” “shortcomings,” “inadequacies,” “flaws,” “weaknesses,” “constraints,” “deficiencies,” “problems,” and “drawbacks” in the search. Limitations not mentioned were found by reading the paper and assigning type and frequency. The number of hedging and weasel words used to describe the conclusion or validate findings was determined by reading the article and adding them up.

For JSLS , there were 129 articles having 63 different types of limitations. Authors claimed 476, and an additional 32 were found within the article, totaling 508 limitations (93.7% admitted to and 6.3% discovered that were not mentioned). This was a 3.9 limitation average per article. No article said it was free of limitations. The ten most frequent limitations and their rate of occurrence are in Table 1 . The total number of limitations, frequency, and visual depictions are seen in Figures 1A and 1B .

The Ten Most Frequent Limitations Found in JSLS and Surg Endosc Articles

( A ) Visual depiction of the ranked frequency of limitations for JSLS articles reviewed.

There were 169 articles for Surg Endosc , with 78 different named limitations the authors claimed for a total of 1,162. An additional 94 limitations were found in the articles, totaling 1,256, or 7.4 per article. The authors explicitly stated 92.5% of the limitations, and an additional 7.5% of additional limitations were found within the article. Five claimed zero limitations (5/169 = 3%). The ten most frequent limitations and their rate of occurrence are in Table 1 . The total number of limitations and frequency is shown in Figures 1A and 1B .

Conclusions were described in hedged, weasel words or words of estimative probability 95.6% of the time (285/298).

A research hypothesis aims to test the idea about expected relationships between variables or to explain an occurrence. The assessment of a hypothesis with limitations embedded in the method reaches a conclusion that is inherently flawed. What is compromised by the limitation(s)? The result is an inferential study in the presence of uncertainty. As the number of limitations increases, the validity of information decreases due to the proliferation of uncertain information. Information gathered and conclusions made in the presence of limitations can be functionally unsound. Hypothesis testing of spurious conditions with limitations and then claiming a conclusion is not a reliable method for generating factual evidence. The authors’ reliance on limitation gathered “evidence” data and asserting that this is valid is spurious reasoning. The bridge between theory and evidence is not through limitations that unquestionably accept findings. A range of conclusion possibilities exists being some percent closer to either more correct or incorrect. Relying on leveraging the pursuit of “fact” in the presence of limitations as the safeguard is akin to the fox watching the hen house. Acknowledgment of the uncertainty limitations create in research and discounting the finding’s reliability would give more credibility to the effort. Shortcomings and widespread misuses of research limitation justifications make findings suspect and falsely justified in many instances.

The JSLS instructions to authors say that in the discussion section of the paper the author(s) must “Comment on any methodological weaknesses of the study” ( http://jsls.sls.org/guidelines-for-authors/ ). In their instructions for authors, Surg Endosc says that in the discussion of the paper, “A paragraph discussing study limitations is required” ( https://www.springer.com/journal/464/submission-guidelines ). A comment for a written article about a limitation should express an opinion or reaction. A paragraph discussing limitations, especially, if there is more than one, requires just that: a paragraph and discussion. These requirements were not met or enforced by JSLS 86% (111/129) of the time and 92.3% (156/169) for Surg Endosc . This is an error in peer reviewing, not adhering to established research publication best practices, and the journals needing to adhere to their guidelines. The International Committee of Medical Journal Editors, uniform requirements for manuscripts recommends that authors “State the limitations of your study, and explore the implications of your findings for future research and for clinical practice or policy. Discuss the influence or association of variables, such as sex and/or gender, on your findings, where appropriate, and the limitations of the data.” It also says, “describe new or substantially modified methods, give reasons for using them, and evaluate their limitations” and “Include in the Discussion section the implications of the findings and their limitations, including implications for future research” and “give references to established methods, including statistical methods (see below); provide references and brief descriptions for methods that have been published but are not well known; describe new or substantially modified methods, give reasons for using them, and evaluate their limitations.” 65 “Reporting guidelines (e.g., CONSORT, 1 ARRIVE 2 ) have been proposed to promote the transparency and accuracy of reporting for biomedical studies, and they often include discussion of limitations as a checklist item. Although such guidelines have been endorsed by high-profile biomedical journals, and compliance with them is associated with improved reporting quality, 3 adherence remains suboptimal.” 4 , 5

Limitations start in the methodologic design phase of research. They require troubleshooting evaluations from the start to consider what limitations exist, what is known and unknown, where, and how to overcome them, and how they will affect the reasonableness and assessment of possible conclusions. A named limitation represents a category with numerous components. Each factor has a unique effect on findings and collectively influences conclusion assessment. Even a single limitation can compromise the study’s implementation and adversely influence research parameters, resulting in diminished value of the findings, outcomes, and conclusions. This becomes more problematic as the number of limitations and their components increase. Any limitation influences a research paper. It is unknown how much and to what extent any limitation affects other limitations, but it does create a cascading domino effect of ever-increasing interactions that compromise findings and conclusions. Considering “research” as a system, it has sensitivity and initial conditions (methodology, data collection, analysis, etc.). The slightest alteration of a study due to limitations can profoundly impact all aspects of the study. The presence and influence of limitations introduce a range of unpredictable influences on findings, results, and conclusions.

Researchers and readers need to pay attention to and discount the effects limitations have on the validity of findings. Richard Feynman said in “Cargo cult science” “the first principle is that you must not fool yourself and you are the easiest person to fool.” 73 We strongly believe our own nonsense or wrong-headed reasoning. Buddhist philosophers say we are attached to our ignorance. Researchers are not critical enough about how they fool themselves regarding their findings with known limitations and then pass them on to readers. The competence of findings with known limitations results in suspect conclusions.

Authors should not ask for dismissal, disregard, or indulgence of their limitations. They should be thoughtful and reflective about the implications and uncertainty the limitations create 67 ; their uncertainties, blind spots, and impact on the research’s relevance. A meaningful presentation of study limitations should describe the limitation, explain its effect, provide possible alternative approaches, and describe steps taken to mitigate the limitation. This was largely absent from the articles reviewed.

Authors use synonyms and phrases describing limitations that hide, deflect, downplay, and divert attention from them, i.e., some drawbacks of the study are …, weaknesses of the study are…, shortcomings are…, and disadvantages of the study are…. They then say their finding(s) lack(s) generalizability, meaning the findings only apply to the study participants or that care, sometimes extreme, must be taken in interpreting the results. Which limitation components are they referring to? Are the authors aware of the extent of their limitations, or are they using convenient phrases to highlight the existence of limitations without detailing their defects?

Limitations negatively weigh on both data and conclusions yet no literature exists to provide a quantifiable measure of this effect. The only acknowledgment is that limitations affect research data and conclusions. The adverse effects of limitations are both specific and contextual to each research article and is part of the parameters that affect research. All the limitations are expressed in words, excuses, and a litany of mea culpas asking for forgiveness and without explaining the extent or magnitude of their impact. It is left to the writer and reader to figure out. It is not known what value writers put on their limitations in the 298 articles reviewed from JSLS and Surg Endosc . Listing limitations without comment and effect on the findings and conclusions is a compromising red flag. Therefore, a limitation scoring method was developed and is proposed to assess the level of suspicion generated by the number of limitations.

It is doubtful that a medical research article is so well designed and executed that there are no limitations. This is doubtful since there are unknown unknowns. This study showed that authors need to acknowledge all the limitations when they are known. They acknowledge the ones they know but do not consider other possibilities. There are the known known limitations; the ones the author(s) are aware of and can be measured, some explained, most not. The known unknowns: limitations authors are aware of but cannot explain or quantify. The unknown unknown limitations: the ones authors are not aware of and have unknown influence(s), i.e., the things they do not know they do not know. These are blind spots (not knowing what they do not know or black swan events). And the unknown knowns; the limitations authors may be aware of but have not disclosed, thoroughly reported, understood, or addressed. They are unexpected and not considered. See Table 2 . 74

Limitations of Known and Unknowns as They Apply to Limitations

It is possible that authors did not identify, want to identify, or acknowledge potential limitations or were unaware of what limitations existed. Cumulative complexity is the result of the presence of multiple limitations because of the accumulation and interaction of limitations and their components. Just mentioning a limitation category and not the specific parts that are the limitation(s) is not enough. Authors telling readers of their known research limitations is a caution to discount the findings and conclusions. At what point does the caution for each limitation, its ramifications, and consequences become a warning? When does the piling up of mistakes, bad and missing data, biases, small sample size, lack of generalizability, confounding factors, etc., reach a point when the findings become s uninterpretable and meaningless? “Caution” indicates a level of potential hazard; a warning is more dire and consequential. Authors use the word “caution” not “warning” to describe their conclusions. There is a point when the number of limitations and their cumulative effects surpasses the point where a caution statement is no longer applicable, and a warning statement is required. This is the reason for establishing a limitations risk score.

Limitations put medical research articles at risk. The accumulation of limitations (variables having additional limitation components) are gaps and flaws diluting the probability of validity. There is currently no assessment method for evaluating the effect(s) of limitations on research outcomes other than awareness that there is an effect. Authors make statements warning that their results may not be reliable or generalizable, and need more research and larger numbers. Just because the weight effect of any given limitation is not known, explained, or how it discounts findings does not negate a causation effect on data, its analysis, and conclusions. Limitation variables and the ramifications of their effects have consequences. The relationship is not zero effect and accumulates with each added limitation.

As a result of this research, a limitation index score (LIS) system and assessment tool were developed. This limitation risk assessment tool gives a scores assessment of the relative validity of conclusions in a medical article having limitations. The adoption of the LIS scoring assessment tool for authors, researchers, editors, reviewers, and readers is a step toward understanding the effects of limitations and their causal relationships to findings and conclusions. The objective is cleaner, tighter methodologies, and better data assessment, to achieve more reliable findings. Adjustments to research conclusions in the presence of limitations are necessary. The degree of modification depends on context. The cumulative effect of this burden must be acknowledged by a tangible reduction and questioning of the legitimacy of statements made under these circumstances. The description calculating the LIS score is detailed in Appendix 1 .

A limitation word or phrase is not one limitation; it is a group of limitations under the heading of that word or phrase having many additional possible components just as an individual named influence. For instance, when an admission of selection bias is noted, the authors do not explain if it was an exclusion criterion, self-selection, nonresponsiveness, lost to follow-up, recruitment error, how it affects external validity, lack of randomization, etc., or any of the least 263 types of known biases causing systematic distortions of the truth whether unintentional or wanton. 40 , 76 Which forms of selection bias are they identifying? 63 Limitations have branches that introduce additional limitations influencing the study’s ability to reach a useful conclusion. Authors rarely tell you the effect consequences and extent limitations have on their study, findings, and conclusions.

This is a sample of limitations and a few of their component variables under the rubric of a single word or phrase. See Table 3 .

A Limitation Word or Phrase is a Limitation Having Additional Components That Are Additional Limitations. When an Author Uses the Limitation Composite Word or Phrase, They Leave out Which One of Its Components is Contributory to the Research Limitations. Each Limitation Interacts with Other Limitations, Creating a Cluster of Cross Complexities of Data, Findings, and Conclusions That Are Tainted and Negatively Affect Findings and Conclusions

Limitations rarely occur alone. If you see one there are many you do not see or appreciate. Limitation s components interact with their own and other limitations, leading to complex connections interacting and discounting the reliability of findings. By how much is context dependent: but it is not zero. Limitations are variables influencing outcomes. As the number of limitations increases, the reliability of the conclusions decreases. How many variables (limitations) does it take to nullify the claims of the findings? The weight and influence of each limitation, its aggregate components, and interconnectedness have an unknown magnitude and effect. The result is a disorderly concoction of hearsay explanations. Table 4 is an example of just two single explanation limitations and some of their components illustrating the complex compounding of their effects on each other.

An Example of Interactions between Only Two Limitations and Some of Their Components Causes 16 Interactions

The novelty of this paper on limitations in medical science is not the identification of research article limitations or their number or frequency; it is the recognition of the multiplier effect(s) limitations and the influence they have on diminishing any conclusion(s) the paper makes. It is possible that limitations contribute to the inability of studies to replicate and why so many are one-time occurrences. Therefore, the generalizability statement that should be given to all readers is BEWARE THERE IS A REDUCTION EFFECT ON THE CONCLUSIONS IN THIS ARTICLE BECAUSE OF ITS LIMITATIONS.

Journals accept studies done with too many limitations, creating forking path situations resulting in an enormous number of possible associations of individual data points as multiple comparisons. 79 The result is confusion, a muddled mess caused by interactions of limitations undermining the ability to make valid inferences. Authors know and acknowledge but rarely explain them or their influence. They also use incomplete and biased databases, biased methods, small sample sizes, and not eliminating confounders, etc., but persist in doing research with these circumstances. Why is that? Is it because when limitations are acknowledged, authors feel justified in their conclusions? It wasn’t my poor research design; it was the limitation(s). How do peer reviewers score and analyze these papers without a method to discount the findings and conclusions in the presence of limitations? What are the calculus editors use to justify papers with multiple limitations, reaching compromised or spurious conclusions? How much caution or warning should a journal say must be taken in interpreting article results? How much? Which results? When? Under what circumstance(s)?

Since a critical component of research is its limitations, the quality and rigor of research are largely defined by, 75 these constraints making it imperative that limitations be exposed and explained. All studies have limitations admitted to or not, and these limitations influence outcomes and conclusions. Unfortunately, they are given insufficient attention, accompanied by feeble excuses, but they all matter. The degrees of freedom of each limitation influence every other limitation, magnifying their ramifications and confusion. Limitations of a scientific article must put the findings in context so the reader can judge the validity and strength of the conclusions. While authors acknowledge the limitations of their study, they influence its legitimacy.

Not only are limitations not properly acknowledged in the scientific literature, 8 but their implications, magnitude, and how they affect a conclusion are not explained or appreciated. Authors work at claiming their work and methods “overcome,” “avoid,” or “circumvent” limitations. Limitations are explained away as “Failure to prove a difference does not prove lack of a difference.” 60 Sample size, bias, confounders, bad data, etc. are not what they seem and do not sully the results. The implication is “trust me.” But that’s not science. Limitations create cognitive distortions and framing (misperception of reality) for the authors and readers. Data in studies with limitations is data having limitations. It was real but tainted.

Limitations are not a trivial aspect of research. It is a tangible something, positive or negative, put into a data set to be analyzed and used to reach a conclusion. How did these extra somethings, known unknowns, not knowns, and unknown knowns, affect the validity of the data set and conclusions? Research presented with the vagaries of explicit limitations is intensified by additional limitations and their component effects on top of the first limitation s , quickly diluting any conclusion making its dependability questionable.

This study’s analysis of limitations in medical articles averaged 3.9% per article for JSLS and 7.4% for Surg Endosc . Authors admit to some and are aware of limitations, but not all of them and discount or leave out others. Limitations were often presented with misleading and hedging language. Authors do not give weight or suggest the percent discount limitations have on the reliance of conclusion(s). Since limitations influence findings, reliability, generalizability, and validity without knowing the magnitude of each and their context, the best that can be said about the conclusions is that they are specific to the study described, context-driven, and suspect.

Limitations mean something is missing, added, incorrect, unseen, unaware of, fabricated, or unknown; circumstances that confuse, confound, and compromise findings and information to the extent that a notice is necessary. All medical articles should have this statement, “Any conclusion drawn from this medical study should be interpreted considering its limitations. Readers should exercise caution, use critical judgement, and consult other sources before accepting these findings. Findings may not be generalizable regardless of sample size, composition, representative data points, and subject groups. Methodologic, analytic, and data collection may have introduced biases or limitations that can affect the accuracy of the results. Controlling for confounding variables, known and unknown, may have influenced the data and/or observations. The accuracy and completeness of the data used to draw a conclusion may not be reliable. The study was specific to time, place, persons, and prevailing circumstances. The weight of each of these factors is unknown to us. Their effect may be limited or compounded and diminish the validity of the proposed conclusions.”

This study and findings are limited and constrained by the limitations of the articles reviewed. They have known and unknown limitations not accounted for, missing data, small sample size, incongruous populations, internal and external validity concerns, confounders, and more. See Tables 2 and 3 . Some of these are correctible by the author’s awareness of the consequences of limitations, making plans to address them in the methodology phase of hypothesis assessment and performance of the research to diminish their effects.

Limitations in research articles are expected, but they can be reduced in their effect so that conclusions are closer to being valid. Limitations introduce elements of ignorance and suspicion. They need to be explained so their influence on the believability of the study and its conclusions is closer to meeting construct, content, face, and criterion validity. As the number of limitations increases, common sense, skepticism, study component acceptability, and understanding the ramifications of each limitation are necessary to accept, discount, or reject the author’s findings. As the number of hedging and weasel words used to explain conclusion(s) increases, believability decreases, and raises suspicion regarding claims. Establishing a systematic limitation scoring index limitations for authors, editors, reviewers, and readers and recognizing their cumulative effects will result in a clearer understanding of research content and legitimacy.

How to calculate the Limitation Index Score (LIS). See Tables 5 – 5 . Each limitation admitted to by authors in the article equals (=) one (1) point. Limitations may be generally stated by the author as a broad category, but can have multiple components, such as a retrospective study with these limitation components: 1. data or recall not accurate, 2. data missing, 3. selection bias not controlled, 4. confounders not controlled, 5. no randomization, 6. no blinding, 7. difficult to establish cause and effect, and 8. cannot draw a conclusion of causation. For each component, no matter how many are not explained and corrected, add an additional one (1) point to the score. See Table 2 .

The Limitation Scoring Index is a Numeric Limitation Risk Assessment Score to Rank Risk Categories and Discounting Probability of Validity and Conclusions. The More Limitations in a Study, the Greater the Risk of Unreliable Findings and Conclusions

Limitations May Be Generally Stated by the Author but Have Multiple Components, Such as a Retrospective Study Having Disadvantage Components of 1. Data or Recall Not Accurate, 2. Data Missing, 3. Selection Bias Not Controlled, 4. Confounders Not Controlled, 5. No Randomization, 6. No Blinding, 7 Difficult to Establish Cause and Effect, 8. Results Are Hypothesis Generating, and 9. Cannot Draw a Conclusion of Causation. For Each Component, Not Explained and Corrected, Add an Additional One (1) Point Is Added to the Score. Extra Blanks Are for Additional Limitations

An Automatic 2 Points is Added for Meta-Analysis Studies Since They Have All the Retrospective Detrimental Components. 44 Data from Insurance, State, National, Medicare, and Medicaid, Because of Incorrect Coding, Over Reporting, and Under-Reporting, Etc. Each Component of the Limitation Adds One Additional Point. For Surveys and Questionnaires Add One Additional Point for Each Bias. Extra Blanks Are for Additional Limitations

Automatic Five (5) Points for Manufacturer and User Facility Device Experience (MAUDE) Database Articles. The FDA Access Data Site Says Submissions Can Be “Incomplete, Inaccurate, Untimely, Unverified, or Biased” and “the Incidence or Prevalence of an Event Cannot Be Determined from This Reporting System Alone Due to Under-Reporting of Events, Inaccuracies in Reports, Lack of Verification That the Device Caused the Reported Event, and Lack of Information” and “DR Data Alone Cannot Be Used to Establish Rates of Events, Evaluate a Change in Event Rates over Time or Compare Event Rates between Devices. The Number of Reports Cannot Be Interpreted or Used in Isolation to Reach Conclusions” 80

Total Limitation Index Score

Each limitation not admitted to = two (2) points. A meta-analysis study gets an automatic 2 points since they are retrospective and have detrimental components that should be added to the 2 points. Data from insurance, state, national, Medicare, and Medicaid, because of incorrect coding, over-reporting, and underreporting, etc., score 2 points, and each component adds one additional point. Surveys and questionnaires get 2 points, and add one additional point for each bias. See Table 3 .

Manufacturer and User Facility Device Experience (MAUDE) database articles receive an automatic five (5) points. The FDA access data site says, submissions can be “incomplete, inaccurate, untimely, unverified, or biased” and “the incidence or prevalence of an event cannot be determined from this reporting system alone due to underreporting of events, inaccuracies in reports, lack of verification that the device caused the reported event, and lack of information” and “MDR data alone cannot be used to establish rates of events, evaluate a change in event rates over time or compare event rates between devices. The number of reports cannot be interpreted or used in isolation to reach conclusions.” 80 See Table 4 . Add one additional point for each additional limitation noted in the article.

Add one additional point for each additional limitation and one point for each of its components. Extra blanks are for additional

limitations and their component scores.

Funding sources: none.

Disclosure: none.

Conflict of interests: none.

Acknowledgments: Author would like to thank Lynda Davis for her help with data collection.

References:

All references have been archived at https://archive.org/web/

• 1. Schulz K, Altman D, Moher D, CONSORT Group. CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials. BMJ. 2010;340:c332. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 2. Kilkenny C, Browne WJ, Cuthill IC, Emerson M, Altman DG. Improving bioscience research reporting: the ARRIVE guidelines for reporting animal research. PLoS Biol. 2010;8(6):e1000412. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 3. Kane R, Kane RL, Wang J, Garrard J. Reporting in randomized clinical trials improved after adoption of the CONSORT statement. J Clin Epidemiol. 2007;60(3):241–249. [ DOI ] [ PubMed ] [ Google Scholar ]
• 4. Turner L, Turner L, Shamseer L, Altman DG, Schulz KF, Moher D. Does use of the CONSORT Statement impact the completeness of reporting of randomised controlled trials published in medical journals? A Cochrane review. Syst Rev. 2012;1:60. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 5. Kilicoglu H, Rosemblat G, Malicki M, ter Riet G. Automatic recognition of self-acknowledged limitations in clinical research literature. J AM Med Inform Assoc. 2018;25(7):855–861. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 6. Ross P, Zaidi N. Limited by our limitations. Perspect Med Educ. 2019;8(4):261–264. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 7. Ioannidis J. Why most published research findings are false. PLoS Med. 2005;2(8):e124. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 8. Ioannidis J. Limitations are not properly acknowledged in the scientific literature. J Clin Epidemiol. 2007;60(4):324–329. [ DOI ] [ PubMed ] [ Google Scholar ]
• 9. Puhan MA, Akl EA, Bryant D, Xie F, Apolone G, ter Riet G. Discussing study limitations in reports of biomedical studies-the need for more transparency. Health Qual Life Outcomes. 2012;10:23. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 10. Greener S. Research limitations: the need for honesty and common sense. Interactive Learning in Environments. 2018;26(5):567–568. [ Google Scholar ]
• 11. Puhan MA, Heller N, Joleska I, et al. Acknowledging limitations in biomedical studies: the ALIBI study. The Sixth International Congress on Peer Review and Biomedical Publication Vancouver, Canada: JAMA and BMJ, 2009 [ Google Scholar ]
• 12. Guyatt G, Oxman A, Kunz R, et al.; GRADE Working Group. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. Bmj. 2008;336(7650):924–926. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 13. Guyatt GH, Oxman AD, Kunz R, Vist GE, Falck-Ytter Y, Schünemann HJ; GRADE Working Group. What is “quality of evidence” and why is it important to clinicians? Bmj. 2008;336(7651):995–998. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 14. Imrey P. Limitations of meta-analyses of studies with high heterogeneity. JAMA Netw Open. 2020;3(1):e1919325. [ DOI ] [ PubMed ] [ Google Scholar ]
• 15. Schroll J, Moustgaard R, Gøtzsche P. Dealing with substantial heterogeneity in Cochrane reviews: cross-sectional study. BMC Med Res Methodol. 2011;11:22. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 16. Alba A, Alexander P, Chang J, MacIsaac J, DeFry S, Guyatt G. High statistical heterogeneity is more frequent in meta-analysis of continuous than binary outcomes. J Clin Epidemiol. 2016;70:129–135. [ DOI ] [ PubMed ] [ Google Scholar ]
• 17. Serghiou S, Goodman S. Random-effects meta-analysis: summarizing evidence with caveats. JAMA. 2019;321(3):301–302. [ DOI ] [ PubMed ] [ Google Scholar ]
• 18. Presser S. The role of doubt in conceiving research: reflections from a career shaped by a dissertation. Annu Rev Sociol. 2022;48(1):1–21. [ Google Scholar ]
• 19. Easterbrook PJ, Berlin JA, Gopalan R, Matthews DR. Publication bias in clinical research. Lancet. 1991;337(8746):867–872. [ DOI ] [ PubMed ] [ Google Scholar ]
• 20. Hemkens L, Contopoulos-Ioannidis D, Ioannidis J. Routine collected data and comparative effectiveness evidence: promises and limitations. CMAJ. 2016;188(8):E158–E164. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 21. Kaplan R, Chambers D, Glasgow R. Big data and large sample size: a cautionary note on the potential for bias. Clin Transl Sci. 2014;7(4):342–346. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 22. Bradley S, DeVito N, Lloyd K, et al. Reducing bias and improving transparency in medical research: a critical overview of the problems, progress and suggested next steps. J R Soc Med. 2020;113(11):433–443. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 23. Wang M, Bolland M, Grey A. Reporting of limitations of observational research. Jama Intern Med. 2015;175(9):1571–1572. [ DOI ] [ PubMed ] [ Google Scholar ]
• 24. Kukull W, Ganguli M. Generalizability. Neurology. 2012;78(23):1886–1891. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 25. Talari K, Goyal M. Retrospective studies – utility and caveats. J R Coll Physicians Edinb. 2020;50(4):398–402. [ DOI ] [ PubMed ] [ Google Scholar ]
• 26. Tofthagen C. Threats to validity in retrospective studies. J Adv Pract Oncol. 2012;3(3):181–183. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 27. Boston University Cohort studies. Available at: https://sphweb.bumc.bu.edu/otlt/mph-modules/ep/ep713_cohortstudies/index.html .
• 28. Röhrig B, Du Prel J, Wachtlin D, Kwiecien R, Blettner M. Small size calculation in clinical trials. Dtsch Arztebl Int. 2010;107(31–32):552–6. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2933537/pdf/Dtsch_Arztebl_Int-107-0552.pdf . [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 29. Vasileiou K, Barnet J, Thorpe S, Young T. Characterizing and justifying sample size sufficiency in interview-based studies: systematic analysis of qualitative health research over a 15-year period. BMC Medical Research Metholology. 2018;18:148. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 30. Button K, Ioannidis J, Mokrysz C, et al. Power failure: why small sample size undermines the reliability of neuroscience. Nat Rev Neurosci. 2013;14(5):365–376. [ DOI ] [ PubMed ] [ Google Scholar ]
• 31. Faber J, Fonseca L. How sample size influences research outcomes. Dental Press J Orthod. 2014;19(4):27–9. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 32. Nosek B, Spies J, Motyl M. Scientific utopia: II. Restructuring incentives and practices to promote truth over publishability. Perspect Psychol Sci. 2012;7(6):615–631. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 33. Jager KJ, Tripepi G, Chesnaye NC, Dekker FW, Zoccali C, Stel VS. Where to look for the most frequent biases? Nephrology (Carlton). 2020;25(6):435–441. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 34. Lambert J. How to assess bias in clinical studies? Clin Orthop Relat Res. 2011;469(6):1794–1796. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 35. Croskerry P. 50 Cognitive and affective biases in medicine. Critical Thinking Program . Dalhousie University: Halifax, Nova Scotia. Available at: https://sjrhem.ca/wp-content/uploads/2015/11/CriticaThinking-Listof50-biases.pdf . [ Google Scholar ]
• 36. Pannucci C, Wilkins E. Identifying and avoiding bias in research. Plast Reconstr Surg. 2010;126(2):619–625. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 37. Heick T. The cognitive biases list: a visual of 180+ heuristics. Available at: https://www.teachthought.com/critical-thinking/cognitive-biases/ .
• 38. Munafò M, Nosek B, Bishop D, et al. A manifesto for reproducible science. Nat Hum Behav. 2017;1:0021. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 39. Murad M, Chu H, Lin L, Wang Z. The effect of publication bias magnitude and direction on the certainty in evidence. BMJ Evid Based Med. 2018;23(3):84–86. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 40. Hammond M, Stehlik J, Drakos S, Kfoury A. Bias in medicine: lessons learned and mitigation strategies. J Am Coll Cardiol Basic Trans Science. 2021;6:78–85. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 41. Doherty T, Carroll A. Believing in overcoming cognitive biases. AMA J Ethics. 2020;22(9):E773–778. Available at: https://journalofethics.ama-assn.org/sites/journalofethics.ama-assn.org/files/2020-08/medu1-2009.pdf [ DOI ] [ PubMed ] [ Google Scholar ]
• 42. Tipton E, Hallberg K, Chan W. Implications of small samples for generalization adjustments and rules of thumb. Available at: https://journals.sagepub.com/doi/10.1177/0193841X16655665?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed or https://files.eric.ed.gov/fulltext/ED562348.pdf . [ DOI ] [ PubMed ]
• 43. Alvarez G, Núñez-Cortés R, Solà I, et al. Sample size, study length, and inadequate controls were the most common self-acknowledged limitations in manual therapy trials: a methodological review. J Clin Epidemiol. 2021;130:96–106. Available at: 10.1016/j.jclinepi.2020.10.018 or https://www.comecollaboration.org/es/wp-content/uploads/sites/5/2020/11/1-s2.0-S0895435620311574-main-2.pdf . [ DOI ] [ PubMed ] [ Google Scholar ]
• 44. Walker E, Hernandez AV, Kattan MW. Meta-analysis: its strengths and limitations. Cleve Clin J Med. 2008;75(6):431–439. [ DOI ] [ PubMed ] [ Google Scholar ]
• 45. Epidemiology for the Uninitiated. Available at: https://www.bmj.com/about-bmj/resources-readers/publications/epidemiology-uninitiated .
• 46. Research Guides USC Libraries. Available at: https://libguides.usc.edu/writingguide/limitations#:∼:text=Definition,the%20findings%20from%20your%20research .
• 47. Fanelli D. Negative results are disappearing from disciplines and countries. Scientometrics. 2012;90(3):891–904. Available at: https://devaka.info/wp-content/uploads/2016/08/Fanelli12-NegativeResults.pdf . [ Google Scholar ]
• 48. Begg C, Berlin J. Publication bias: a problem in interpreting medical data. Journal of the Royal Statistical Society Series A; Statistics in Society. 1988;151(3):419–445. [ Google Scholar ]
• 49. Mlinaic A, Horvat M, Smolcic V. Dealing with the positive publication bias: why you should really publish your negative results. Biochem Med (Zagreb). 2017;27:447–452. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 50. Nathan H, Pawlik TM. Limitations of claims and registry data in surgical oncology research. Ann Surg Oncol. 2008;15(2):415–423. [ DOI ] [ PubMed ] [ Google Scholar ]
• 51. Bagaev E, Ali A, Saha S, et al. Hybrid surgery for severe mitral valve calcification: limitations and caveats for an open transcatheter approach. Medicina. 2022;58(1):93. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 52. Ng T, McGory M, Ko C, Maggard M. Meta-analysis in surgery methods and limitations. Arch Surg. 2006;141(11):1125–30; discussion 1131. [ DOI ] [ PubMed ] [ Google Scholar ]
• 53. ter Riet G, Chesley P, Gross AG, et al. All that glitters isn’t gold: a survey on acknowledgment of limitations in biomedical studies. PLoS One. 2013;8(11):e73623. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 54. Nunan D, Bankhead C, Aronson J. Selection bias. Catalogue of Bias. 2017. Available at: https://catalogofbias.org/biases/selection-bias/ and https://catalogofbias.org/ . [ DOI ] [ PubMed ]
• 55. Bornhöft G, Maxion-Bergemann S, Wolf U, et al. Checklist for the qualitative evaluation of clinical studies with particular focus on external validity and model validity. BMC Med Res Methodol. 2006;6:56. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 56. Gray J. Discussion and conclusion. AME Med J. 2019;4:26–26. Available at: https://amj.amegroups.org/article/view/4955/pdf . [ Google Scholar ]
• 57. Yavchitz A, Ravaud P, Hopewell S, Baron G, Boutron I. Impact of adding a limitations section to abstracts of systematic reviews on readers’ interpretation: a randomized controlled trial. BMC Med Res Methodol. 2014;14:123. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 58. Keserlioglu K, Kilicoglu H, ter Riet G. Impact of peer review on discussion of study limitations and strength of claims in randomized trial reports: a before and after study. Res Integr Peer Rev. 2019;4:19. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 59. Morris A, Ioannidis J. Limitations of medical research and evidence at the patient-clinician encounter scale. Chest. 2013;143(4):1127–1135. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 60. Lambert W, Janniger E. Limitations of randomized, controlled, double-blinded studies in determining safety and effectiveness of treatments. Curr Med Res Opin. 2022;38(6):1045–1046. [ DOI ] [ PubMed ] [ Google Scholar ]
• 61. Mohseni M, Ameri H, Arab-Zozani M. Potential limitations in systematic review studies assessing the effect of the main intervention for treatment/therapy of COVID-19 patients: an overview. Front Med (Lausanne)). 2022;9:966632. Available at: https://www.frontiersin.org/articles/10.3389/fmed.2022.966632/full . [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 62. Hartman J, Forsen J, Wallace M, Neely G. Tutorial in clinical research: part IV: recognizing and controlling bias. Laryngoscope. 2002;112(1):23–31. [ DOI ] [ PubMed ] [ Google Scholar ]
• 63. Delgado-Rodríguez M, Llorca J. Bias. J Epidemiol Community Health. 2004;58:635–41. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 64. Emerson G, Warme W, Wolf F, Heckman J, Brand R, Leopold S. Testing for the presence of positive-outcome bias in peer review: a randomized controlled trial. Arch Intern Med. 2010;170(21):1934–1939. [ DOI ] [ PubMed ] [ Google Scholar ]
• 65. International Committee of Medical Journal Editors. Uniform requirements for manuscripts submitted to biomedical journals. N Engl J Med. 1997;336(4):309–315. [ DOI ] [ PubMed ] [ Google Scholar ]
• 66. Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals. Updated May 2023. Available at: https://www.icmje.org/icmje-recommendations.pdf . [ PubMed ]
• 67. Lingard L. The art of limitations. Perspect Med Educ. 2015;4(3):136–7. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 68. Infante-Rivard C, Cusson A. Reflection on modern methods: selection bias – a review of recent developments. Int J Epidemiol. 2018;47(5):1714–1722. [ DOI ] [ PubMed ] [ Google Scholar ]
• 69. Garrubba M, Joseph C, Melder A. Best practice to identify and prevent cognitive bias in clinical decision-making: scoping review. Centre for Clinical Effectiveness, Monash Innovation and Quality, Monash Health, Melbourne, Australia. Available at: https://dl.pezeshkamooz.com/pdf/cme/MedicalErrors/cognitive-bias-Dr.moradi.pdf . [ Google Scholar ]
• 70. McGauran N, Wieseler B, Kreis J, Schüler Y-B, Kölsch H, Kaiser T. Reporting bias in medical research - a narrative review. Trials. 2010;11(1):37. Available at: https://trialsjournal.biomedcentral.com/articles/10.1186/1745-6215-11-37?ref=data.gripe . [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 71. Morgado F, Meireles J, Neves C, Amaral A, Serreira M. Scale development: ten main limitations and recommendations to improve future research practices. Psicologia: Reflexao e Critica. 2017;30(3). Available at: https://www.scielo.br/j/prc/a/M6fHHwfVFM9GkjCrsr9SFHz/?lang=en . [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 72. Sheridan D, Julian D. Achievements and limitations of evidence-based medicine. J Am Coll Cardiol. 2016;68(2):204–213. [ DOI ] [ PubMed ] [ Google Scholar ]
• 73. Feynman R. Cargo cult science. Engineering and Science. 1974;37:10–13. Available at: http://calteches.library.caltech.edu/51/2/CargoCult.pdf . [ Google Scholar ]
• 74. U.S. Department of Defense News Transcript. February 12 2002. Available at: https://archive.ph/20180320091111/http://archive.defense.gov/Transcripts/Transcript.aspx?TranscriptID=2636 .
• 75. Resnik D, Shamoo A. Reproducibility and research integrity. Account Res. 2017;24(2):116–123. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5244822/pdf/nihms841390.pdf . [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 76. Hegedus E, Moody J. Clinimetrics corner: the many faces of selection bias. J Man Manip Ther. 2010;18(2):69–73. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 77. Gelman A, Loken E. The statistical crisis in science. Am Sci. 2014;102(6):460–465. Available at: http://www.psychology.mcmaster.ca/bennett/psy710/readings/gelman-loken-2014.pdf . [ Google Scholar ]
• 78. Ott D. Hedging, weasel words, and truthiness and scientific writing. JSLS. 2018;22(4):e2018. 00063. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 79. Ott D. Words representing numeric probabilities in medical writing are ambiguous and misinterpreted. JSLS. 2021;25(3):e2021. 00034. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 80. U.S. Food & Drug Administration MAUDE. Manufacturer and user facility device experience. Available at: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfmaude/textsearch.cfm .
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Research Limitations & Delimitations

By: Derek Jansen (MBA) | Expert Reviewed By: David Phair (PhD) | September 2022

Overview: Limitations vs Delimitations

• Are they the same?
• What are research limitations
• What are research delimitations
• Limitations vs delimitations

First things first…

Let’s start with the most important takeaway point of this post – research limitations and research delimitations are not the same – but they are related to each other (we’ll unpack that a little later). So, if you hear someone using these two words interchangeably, be sure to share this post with them!

Research Limitations

Research limitations are, at the simplest level, the weaknesses of the study , based on factors that are often outside of your control as the researcher. These factors could include things like time , access to funding, equipment , data or participants . For example, if you weren’t able to access a random sample of participants for your study and had to adopt a convenience sampling strategy instead, that would impact the generalizability of your findings and therefore reflect a limitation of your study.

Research limitations can also emerge from the research design itself . For example, if you were undertaking a correlational study, you wouldn’t be able to infer causality (since correlation doesn’t mean certain causation). Similarly, if you utilised online surveys to collect data from your participants, you naturally wouldn’t be able to get the same degree of rich data that you would from in-person interviews .

Simply put, research limitations reflect the shortcomings of a study , based on practical (or theoretical) constraints that the researcher faced. These shortcomings limit what you can conclude from a study, but at the same time, present a foundation for future research . Importantly, all research has limitations , so there’s no need to hide anything here – as long as you discuss how the limitations might affect your findings, it’s all good.

Research Delimitations

Alright, now that we’ve unpacked the limitations, let’s move on to the delimitations .

Research delimitations are similar to limitations in that they also “ limit ” the study, but their focus is entirely different. Specifically, the delimitations of a study refer to the scope of the research aims and research questions . In other words, delimitations reflect the choices you, as the researcher, intentionally make in terms of what you will and won’t try to achieve with your study. In other words, what your research aims and research questions will and won’t include.

As we’ve spoken about many times before, it’s important to have a tight, narrow focus for your research, so that you can dive deeply into your topic, apply your energy to one specific area and develop meaningful insights. If you have an overly broad scope or unfocused topic, your research will often pull in multiple, even opposing directions, and you’ll just land up with a muddy mess of findings .

So, the delimitations section is where you’ll clearly state what your research aims and research questions will focus on – and just as importantly, what they will exclude . For example, you might investigate a widespread phenomenon, but choose to focus your study on a specific age group, ethnicity or gender. Similarly, your study may focus exclusively on one country, city or even organization. As long as the scope is well justified (in other words, it represents a novel, valuable research topic), this is perfectly acceptable – in fact, it’s essential. Remember, focus is your friend.

Need a helping hand?

Conclusion: Limitations vs Delimitations

Ok, so let’s recap.

Research limitations and research delimitations are related in that they both refer to “limits” within a study. But, they are distinctly different. Limitations reflect the shortcomings of your study, based on practical or theoretical constraints that you faced.

Contrasted to that, delimitations reflect the choices that you made in terms of the focus and scope of your research aims and research questions. If you want to learn more about research aims and questions, you can check out this video post , where we unpack those concepts in detail.

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19 Comments

Good clarification of ideas on how a researcher ought to do during Process of choice

Thank you so much for this very simple but explicit explanation on limitation and delimitation. It has so helped me to develop my masters proposal. hope to recieve more from your site as time progresses

Thank you for this explanation – very clear.

Thanks for the explanation, really got it well.

This website is really helpful for my masters proposal

Thank you very much for helping to explain these two terms

I spent almost the whole day trying to figure out the differences

when I came across your notes everything became very clear

thanks for the clearly outlined explanation on the two terms, limitation and delimitation.

Very helpful Many thanks 🙏

Excellent it resolved my conflict .

I would like you to assist me please. If in my Research, I interviewed some participants and I submitted Questionnaires to other participants to answered to the questions, in the same organization, Is this a Qualitative methodology , a Quantitative Methodology or is it a Mixture Methodology I have used in my research? Please help me

How do I cite this article in APA format

Really so great ,finally have understood it’s difference now

Getting more clear regarding Limitations and Delimitation and concepts

I really appreciate your apt and precise explanation of the two concepts namely ; Limitations and Delimitations.

This is a good sources of research information for learners.

thank you for this, very helpful to researchers

Very good explained

Great and clear explanation, after a long confusion period on the two words, i can now explain to someone with ease.

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Research Limitations

It is for sure that your research will have some limitations and it is normal. However, it is critically important for you to be striving to minimize the range of scope of limitations throughout the research process.  Also, you need to provide the acknowledgement of your research limitations in conclusions chapter honestly.

It is always better to identify and acknowledge shortcomings of your work, rather than to leave them pointed out to your by your dissertation assessor. While discussing your research limitations, don’t just provide the list and description of shortcomings of your work. It is also important for you to explain how these limitations have impacted your research findings.

Your research may have multiple limitations, but you need to discuss only those limitations that directly relate to your research problems. For example, if conducting a meta-analysis of the secondary data has not been stated as your research objective, no need to mention it as your research limitation.

Research limitations in a typical dissertation may relate to the following points:

1. Formulation of research aims and objectives . You might have formulated research aims and objectives too broadly. You can specify in which ways the formulation of research aims and objectives could be narrowed so that the level of focus of the study could be increased.

2. Implementation of data collection method . Because you do not have an extensive experience in primary data collection (otherwise you would not be reading this book), there is a great chance that the nature of implementation of data collection method is flawed.

3. Sample size. Sample size depends on the nature of the research problem. If sample size is too small, statistical tests would not be able to identify significant relationships within data set. You can state that basing your study in larger sample size could have generated more accurate results. The importance of sample size is greater in quantitative studies compared to qualitative studies.

4. Lack of previous studies in the research area . Literature review is an important part of any research, because it helps to identify the scope of works that have been done so far in research area. Literature review findings are used as the foundation for the researcher to be built upon to achieve her research objectives.

However, there may be little, if any, prior research on your topic if you have focused on the most contemporary and evolving research problem or too narrow research problem. For example, if you have chosen to explore the role of Bitcoins as the future currency, you may not be able to find tons of scholarly paper addressing the research problem, because Bitcoins are only a recent phenomenon.

5. Scope of discussions . You can include this point as a limitation of your research regardless of the choice of the research area. Because (most likely) you don’t have many years of experience of conducing researches and producing academic papers of such a large size individually, the scope and depth of discussions in your paper is compromised in many levels compared to the works of experienced scholars.

You can discuss certain points from your research limitations as the suggestion for further research at conclusions chapter of your dissertation.

My e-book,  The Ultimate Guide to Writing a Dissertation in Business Studies: a step by step assistance  offers practical assistance to complete a dissertation with minimum or no stress. The e-book covers all stages of writing a dissertation starting from the selection to the research area to submitting the completed version of the work within the deadline. John Dudovskiy

Academic Writing & Research

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The limitations section: Common Limitations in Research

Every dissertation should include a limitations section in which you recognise the limits and weaknesses of your research, so here are a few tips on what to cover.

Research, by its nature, is a dynamic and iterative process that aims to explore, analyze, and contribute to knowledge in various fields. However, every research endeavour comes with its set of limitations that researchers must acknowledge, address, and navigate. In this blog post, we’ll delve into the common limitations of research and discuss strategies for mitigating their impact on the validity, reliability, and generalizability of findings.

Five main types of limitations

1. sampling limitations:.

• Sample Size: Limited sample size can affect the generalizability and representativeness of research findings. Small samples may not adequately capture the diversity or variability within a population, leading to potential biases or limited statistical power.
• Sampling Bias: Biases in sample selection, such as self-selection bias or sampling from non-representative populations, can compromise the external validity of research outcomes.

2. Measurement and Instrumentation Limitations:

• Measurement Error: Inaccuracies or inconsistencies in measurement instruments, data collection tools, or operational definitions can introduce measurement error, affecting the reliability and validity of results.
• Validity Threats: Threats to internal validity (e.g., confounding variables, selection bias) or external validity (e.g., ecological validity, population validity) can impact the robustness and generalizability of research findings.

3. Methodological Limitations:

• Research Design: Limitations in research design, such as lack of control groups, non-randomized designs, or cross-sectional studies, can constrain the ability to establish causal relationships or infer causality.
• Data Collection Methods: Issues related to data collection methods, such as self-report biases, social desirability biases, or retrospective data, can introduce inaccuracies or distortions in data interpretation.

4. Contextual and External Factors:

• Contextual Constraints: Research conducted in specific contexts or settings may face limitations in generalizing findings to broader populations or different contexts.
• Temporal Limitations: Changes over time, evolving trends, or temporal fluctuations can impact the relevance and applicability of research findings beyond a specific timeframe.

5. Ethical and Practical Constraints:

• Ethical Considerations: Ethical constraints, such as limitations in accessing sensitive data, obtaining informed consent, or ensuring participant confidentiality, can influence the scope and conduct of research.
• Resource Constraints: Practical limitations, such as budget constraints, time constraints, or access to resources (e.g., data, equipment, expertise), can impact the feasibility and scope of research endeavours.

Strategies for Addressing Limitations:

• Transparent Reporting: Clearly articulate and disclose limitations in research methodology, sampling, measurement, and design in research reports, ensuring transparency and accountability.
• Mitigating Biases: Implement strategies to mitigate biases, such as randomization, blinding, control measures, and sensitivity analyses, to enhance the validity and reliability of findings.
• Sensitivity Analyses: Conduct sensitivity analyses or robustness checks to assess the impact of potential biases, outliers, or variations in data on research outcomes.
• Triangulation: Employ triangulation methods, combining multiple data sources, methods, or perspectives, to enhance the validity, reliability, and depth of research findings.
• Longitudinal Studies: Consider longitudinal or follow-up studies to track changes over time, validate findings, and assess the stability of research outcomes.

While every research endeavour has its limitations, acknowledging and addressing these limitations is crucial for maintaining the integrity, rigour, and credibility of research findings. Also, every dissertation should include a limitations section. By adopting transparent reporting practices, implementing mitigation strategies, conducting sensitivity analyses, leveraging triangulation methods, and considering longitudinal approaches, researchers can navigate common limitations effectively and enhance the robustness and applicability of their research contributions.

Posted by, Glenn Stevens

Glenn is an academic writing and research specialist with 15 years experience as a writing coach and PhD supervisor. Also a qualified English teacher, he previously had an extensive career in publishing. He is currently the editor of this website. Glenn lives in the UK. Contact Glenn

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