Glossary of Key Terms
| Term | Definition |
| Pilot study | A small-scale trial run of a planned larger study, conducted to assess whether the full study is feasible and how it should be designed. Also called a feasibility study, feasibility test, pilot experiment, or pilot trial. |
| Feasibility | The degree to which a study can be successfully carried out given its design, resources, recruitment capacity, and protocol. |
| External pilot study | A stand-alone pilot conducted entirely before the main trial; pilot participants’ data are not included in the main trial’s final analysis. |
| Internal pilot study | A pilot phase embedded within the main trial; if no major protocol changes are needed, pilot data are folded into the final analysis. |
| Randomized pilot trial | A small-scale pilot that uses randomization to test allocation, blinding, and adherence procedures for a future randomized controlled trial (RCT). |
| Non-randomized feasibility study | A pilot that tests recruitment, acceptability, and intervention delivery without random allocation; often a precursor to a randomized design. |
| Progression criteria | Pre-specified, measurable benchmarks used to decide whether to proceed with, modify, or abandon the main study after the pilot. |
| Protocol fidelity | The degree to which the study is delivered exactly as planned; tested in the pilot to ensure reproducibility at full scale. |
| Ethical approval (IRB/REC) | Formal clearance from an Institutional Review Board or Research Ethics Committee, required before any human-subjects research begins. |
| Effect size | A statistical measure of the magnitude of a difference or relationship; pilot studies should not be used to generate effect sizes for main-trial power calculations. |
| Contamination | A validity threat that arises when pilot participants are included in the main study, potentially biasing results because they have already been exposed to the intervention. |
Key Takeaways
- A pilot study answers the question ‘Can I do this?’ and not ‘Does this intervention work?’
- Pilot studies have four main types: external, internal, randomized, and non-randomized.
- The primary goal is to test feasibility and acceptability, not to produce statistically significant findings.
- Ethical approval and informed consent are required steps, just as they are for the main study.
- Sample size should be based on practical feasibility goals, not on power calculations.
- Effect sizes from pilot data are unstable and should not be used to power the main trial.
- Common misuses include testing preliminary efficacy, using pilot data to estimate effect sizes, and ignoring poor feasibility signals.
- Findings from a pilot study should lead to a formal go/modify/stop decision for the main study.
- Pilot data should be kept separate from main study data and analyses.
- Lessons learned in pilots, including failures, are publishable and valuable to the research community.
What Is a Pilot Study in Research?
A pilot study is a small-scale trial run of a planned larger study, conducted to assess whether the full study is feasible and how it should be designed. It is a rehearsal, not a performance. The findings are not meant to confirm a hypothesis but to tell the researcher whether the plan is workable.
The terms below are all used to describe essentially the same concept. Recognizing them expands the scope of literature a researcher can draw on:
| Term | Notes |
| Pilot study | Most common term across disciplines |
| Feasibility study | Emphasizes the ‘Can I do this?’ question; used interchangeably in many journals |
| Feasibility test | Common in social science and survey research |
| Pilot experiment | Used in laboratory and experimental contexts |
| Pilot trial | Common in clinical and health research |
Pilot studies are used across healthcare, psychology, public health, social sciences, business, the humanities, and digital health research. They are applicable to both qualitative and quantitative methodologies.
What Is the Core Question a Pilot Study Answers?
The central question is: ‘Can I do this?’ and not ‘Does this work?’ A pilot study is not designed to test whether an intervention is effective. It is designed to test whether the procedures, tools, and logistics needed to run the main study are viable.
The table below shows how feasibility questions translate into measurable outcomes:
| Feasibility Question | What to Measure |
| Can I recruit enough participants? | Screening rate per month; enrollment rate; time from screening to enrollment |
| Can I keep participants in the study? | Retention rates by group; reasons for dropout |
| Will participants do what is asked? | Adherence rates to protocol; session attendance; homework completion rates |
| Can the intervention be delivered as planned? | Protocol fidelity rates; staff competence assessments |
| Are assessments too burdensome? | Completion rate of planned assessments; visit duration; dropout reasons |
| Is the intervention acceptable to participants? | Acceptability ratings; qualitative feedback; preference ratings |
How Is a Pilot Study Different from Similar Studies?
Three study types are often confused with pilot studies. The differences matter for how findings can be interpreted and used:
| Study Type | Purpose | Key Distinction from Pilot |
| Feasibility study | Asks whether a larger study can be done at all | Broader scope; does not necessarily mirror the main study design |
| Exploratory study | Investigates a phenomenon without aiming for conclusive results | No intent to scale up; not a precursor to a specific main trial |
| Proof of concept study | Demonstrates whether a concept or technology is workable | Product- or process-focused; narrower aim than a pilot study |
What Are the Different Types of Pilot Studies?
There are four main types. Choosing the right one depends on the stage of research, the level of certainty about the protocol, and whether pilot participants’ data can realistically be included in the main trial.
| Type | Design | Key Feature | Best Used When |
| External pilot | Stand-alone study before the main trial | Pilot data not included in the main trial analysis | Protocol is untested; changes are expected |
| Internal pilot | First phase embedded within the main trial | Pilot data retained in final analysis if no major changes needed | Protocol is well-developed; changes unlikely |
| Randomized pilot trial | Uses randomization on a small scale | Tests allocation, blinding, and adherence for a future RCT | Planning a randomized controlled trial |
| Non-randomized feasibility study | No random allocation | Tests recruitment, acceptability, and delivery procedures | Early-stage feasibility testing; pre-RCT work |
These categories are important because they determine what conclusions can be drawn from pilot data and how that data may be used when creating the main study protocol.
Objectives of a Pilot Study in Research
A well-designed pilot study addresses five core objectives, all oriented around feasibility rather than hypothesis testing:
| Objective | What It Involves |
| Assess feasibility | Evaluate participant recruitment rates, retention rates, refusal rates, and whether the numbers of participants, researchers, and support staff are adequate. |
| Identify resource requirements | Determine how long the intervention or questionnaire takes to administer, whether software and equipment function as expected, and what monitoring procedures need to be in place. |
| Understand procedural challenges | Surface problems in study design, data collection processes, equipment handling, and logistics before they occur at full scale. |
| Refine data collection instruments | Verify that questionnaires are relevant, clearly worded, and coherently presented; confirm that outcome measures are valid for the target population. |
| Develop good clinical and research practices | Establish documentation procedures, informed consent processes, data collection tools, regulatory reporting workflows, and monitoring systems that will carry through to the main study. |
How to Conduct a Pilot Study: A Step-by-Step Guide
The methodology for a pilot study mirrors the steps of a full-scale study, but on a smaller, exploratory scale. Each step should be documented in a formal pilot protocol.
| Step | Action | Key Considerations |
| 1 | Define objectives | Specify feasibility goals and set pre-specified, quantitative benchmarks (e.g., at least 70% of participants will attend 8 of 12 sessions). Vague objectives produce uninterpretable results. |
| 2 | Design the study | Select a small, representative sample; develop research instruments such as surveys or interview guides; choose whether to randomize. |
| 3 | Obtain ethical approval | Secure clearance from the relevant Institutional Review Board (IRB) or Research Ethics Committee (REC) and obtain informed consent from all participants. This step is mandatory, not optional. |
| 4 | Recruit participants | Use eligibility criteria and sampling strategies that match the main study. The sample should reflect the target population. |
| 5 | Collect data | Administer the intervention or instrument as planned. Document deviations. Collect data on feasibility, acceptability, and appropriateness of procedures and not just on outcomes. |
| 6 | Analyze data | Use descriptive statistics and qualitative feedback. No inferential statistics or hypothesis tests are appropriate. No power analysis is required or recommended. |
| 7 | Report results | Produce a detailed report covering key findings, protocol changes made during the process, feasibility benchmark outcomes, and instruments used. |
| 8 | Make a go/modify/stop decision | Use pre-specified progression criteria to decide whether to proceed as planned, modify the main study design, or stop and redesign. |
What Should Happen After the Pilot Test?
Post-pilot actions are as important as the pilot itself. A pilot that does not lead to explicit design decisions has limited value.
- Locate and document challenges: List every issue or risk identified: recruitment shortfalls, dropout patterns, protocol deviations, equipment failures, or participant burden. Develop a backup plan for each.
- Determine feasibility: Review whether the pilot achieved its pre-specified benchmarks. If not, the study design should be reconsidered before proceeding.
- Refine methods and procedures: Modify data collection instruments such as questionnaires, eligibility criteria, randomization procedures, and outcome measures as needed.
- Prepare a detailed main study plan: Update the full protocol to reflect all changes, including revised timelines, adjusted sample sizes, and corrected consent procedures.
- Keep pilot data separate: Pilot participants’ data should be reported separately and not mixed into the main study results unless the design explicitly incorporates an internal pilot with pre-specified criteria for data inclusion.
Examples of Pilot Studies
The following examples illustrate how pilot study findings drive concrete design changes across different research contexts.
Example 1: Clinical Trial (Drug or Device)
In a pilot randomized controlled trial of a new antihypertensive drug, investigators tested whether clinics could recruit five patients per month, maintain at least 80% medication adherence, and achieve 90% follow-up at three months. The pilot revealed slower-than-expected recruitment and difficulties with home blood pressure monitoring.
Changes made before the main trial:
- Revised participant inclusion criteria to widen the eligible pool
- Simplified home monitoring instructions and provided training sessions
- Extended the planned recruitment timeline by four months
Example 2: Public Health / Behavioural Intervention
A pilot study of a school-based physical activity program evaluated whether teachers would deliver at least three structured activity sessions per week and whether students would tolerate wearable accelerometers. Feasibility outcomes showed good acceptability but low device compliance on certain days.
Changes made before the cluster randomized trial:
- Revised data collection schedules to avoid days with high non-compliance
- Added supplementary teacher training sessions on device use
- Simplified the accelerometer wear protocol for younger students
Example 3: Digital Health / eHealth Tool
Researchers piloted a mobile app for diabetes self-management to test app usability, login frequency, and completeness of glucose logging over four weeks. The pilot identified usability problems on older phones and lower engagement among older adults.
Changes made before the definitive effectiveness study:
- Redesigned the app interface to support older operating systems
- Simplified notification schedules and created tailored onboarding content for older users
- Extended the engagement measurement window from four to eight weeks
Advantages and Disadvantages of Pilot Testing
| Advantages | Disadvantages |
| Identifies flaws in study design, data collection, and instruments before full-scale investment | Requires additional funding, time, and personnel that may divert resources from the main study |
| Allows researchers to refine research questions, eligibility criteria, and randomization procedures | Results from small samples are not generalizable to the broader target population |
| Provides practical insights into participant recruitment and retention strategies | Risk of contamination if pilot participants are included in the main study since they have already been exposed to the intervention |
| Helps ensure the research is ethically sound by surfacing consent and burden issues early | A successful pilot does not guarantee the success of the main study |
| Builds funder, ethics committee, and stakeholder confidence by demonstrating empirical feasibility evidence | Pilot studies lack the statistical power to detect treatment effects or produce reliable effect size estimates |
| Supports development of informed consent procedures, data tools, and monitoring workflows | Problems identified in the pilot are sometimes not acted upon before the main trial begins |
How Do You Critically Appraise a Pilot Study?
Critical appraisal of a pilot study involves evaluating whether it was designed, conducted, and reported in a way that genuinely informs the main study design.
Use the following checklist when reviewing a published or proposed pilot study:
| Appraisal Dimension | Questions to Ask |
| Objectives | Are feasibility objectives clearly stated and measurable? Are progression criteria pre-specified? |
| Design | Does the pilot mirror the intended main study design? Is the sample representative of the target population? |
| Ethical process | Was ethical approval obtained? Was informed consent properly documented? |
| Feasibility outcomes | Are feasibility benchmarks reported (e.g., recruitment rate, retention rate, adherence rate)? Are shortfalls explained? |
| Protocol changes | Does the report describe what was changed as a result of the pilot and why? |
| Statistical analysis | Does the report avoid inappropriate inferential statistics or hypothesis tests? Are effect sizes presented with appropriate caveats? |
| Go/modify/stop decision | Does the report make an explicit, evidence-based recommendation about whether and how to proceed? |
| Utility for others | Are findings reported in enough detail that other researchers doing similar work could benefit? |
How Many Participants Do You Need for a Pilot Study?
There is no universal rule. Sample size in a pilot study should be based on practical considerations, not on power calculations. Because pilot studies are not designed to test hypotheses, a power analysis is neither required nor appropriate.
| Factor | Guidance |
| Participant flow | How many people need to be screened to enroll enough participants? Factor in expected refusal and dropout rates. |
| Budgetary constraints | What is the maximum number of participants the available resources can support? |
| Feasibility benchmark requirements | How many participants are needed to generate a meaningful estimate of recruitment rate, adherence, or dropout? A minimum of 10 is often cited for questionnaire pre-testing; 20–30 is common for intervention-based feasibility studies. |
| Study type | Internal pilots embedded in a main trial may use fewer dedicated pilot participants than stand-alone external pilots. |
A common rule of thumb cited in the literature is 10% of the planned main study sample, but this should always be evaluated against the specific feasibility objectives. The goal is to have enough participants to meaningfully evaluate the feasibility benchmarks, not to achieve statistical significance.
What Are the Common Misuses of Pilot Studies?
Pilot studies are frequently misused in ways that produce unreliable findings and contribute to the failure of subsequent main trials. Awareness of these pitfalls is as important as knowing how to design a good pilot.
Misuse 1: Testing Preliminary Efficacy
Many pilot study protocols propose to evaluate whether the intervention ‘works’. This is inappropriate for two reasons. First, at the time a pilot is conducted, there is insufficient knowledge about whether the intervention was implemented correctly. Second, pilot studies are not powered to answer efficacy questions. Any apparent effect is uninterpretable. It may be a true result, a false positive, or a false negative.
Misuse 2: Using Pilot Data to Estimate Effect Sizes for Power Calculations
Effect size estimates from small pilot samples are statistically unstable. Using them to calculate sample sizes for the main trial typically leads to one of two problems:
- Leads to a main trial that is underpowered and produces a false negative result (overestimated effect size)
- Leads to a main trial that is oversized, wasteful of resources, and potentially unfundable (underestimated effect size)
The recommended approach is to base main-trial power calculations on a clinically or practically meaningful effect size. Effect size should be determined by what difference would actually change clinical practice, policy, or guidelines, rather than on pilot estimates.
Misuse 3: Assessing Safety and Tolerability
Due to small sample sizes, pilot studies cannot provide useful safety data except in extreme cases (e.g., repeated serious adverse events). The absence of a safety signal in a pilot does not mean the intervention is safe. It only means a serious adverse event was not observed in that small group.
Misuse 4: Ignoring Feasibility Signals
Problems identified in the pilot like high dropout, low adherence, or protocol violations, are sometimes not corrected before the main trial is launched. This is a leading cause of main trial failure. Pilot findings should be treated as a serious decision tool, not as a formality.
Misuse 5: Calling a Study a Pilot for the Wrong Reasons
A study should not be called a pilot simply because:
- It is a student or intern project
- It has a small sample due to funding constraints
- A supervisor suggested calling it a pilot
- A similar study was previously published as a pilot
A study is a pilot because it is designed to test feasibility, not because it is small.
| Misuse | The Problem | The Correct Approach |
| Testing preliminary efficacy | Pilot is underpowered; conclusions are premature and uninterpretable | Focus exclusively on feasibility benchmarks |
| Using pilot effect sizes for power calculations | Estimates are unstable; leads to over- or underpowered main trials | Base power calculations on clinically meaningful differences |
| Assessing safety/tolerability | Sample too small to detect all but extreme adverse events | Report adverse event rates with confidence intervals; do not conclude ‘safe’ |
| Ignoring feasibility signals | Poor recruitment or adherence carries over into a failed main trial | Act on every flagged problem before launching the main study |
| Mislabelling small studies as pilots | Obscures the true purpose; produces findings of limited utility | Only use the term ‘pilot’ for studies explicitly designed to test feasibility |
Ethics and Informed Consent in Pilot Studies
Ethical approval is a mandatory step in pilot studies, not an optional one. Because pilot studies involve human participants, all standard research ethics requirements apply.
- IRB/REC approval: Obtain formal clearance from the relevant Institutional Review Board or Research Ethics Committee before any data collection begins.
- Informed consent: All participants must receive a full explanation of the study and provide written consent. The consent document for a pilot should reflect the study’s limited scope if activities differ from the main trial.
- Participant burden: One of the most valuable outputs of a pilot is an assessment of how burdensome the procedures are. If participants find assessments too long or intrusive, this is a critical finding that must be addressed.
- Ethical benefit of piloting: Running a pilot on a small scale before exposing larger numbers of participants to a potentially flawed or unworkable design is itself an ethical act because it protects future participants from unnecessary burden and risk.
- Incentives: Determine appropriate participant compensation during the pilot, as this informs the main study budget and helps assess participation motivation.
Challenges of Pilot Testing in Research
Despite their value, pilot studies face practical and methodological challenges that researchers should anticipate:
- Resource diversion: Pilot studies require time, funding, and personnel. In resource-constrained settings, these demands may compete directly with the main study.
- Limited generalizability: The small sample means that feasibility results may not reflect what will happen in a larger, more diverse population.
- Contamination risk: If pilot participants are included in the main study, they may respond differently because they have already been exposed to the intervention or measurement tools.
- Sunk-cost pressure: When a pilot requires significant investment, research teams may find it difficult to stop and redesign after an unsuccessful outcome.
- Reporting deficiencies: Many published pilot studies do not clearly state feasibility outcomes, pre-specified progression criteria, or how findings changed the main study design. This limits their usefulness to the broader research community.
- Misinterpretation: Researchers sometimes interpret a pilot that ‘went well’ as evidence that the intervention works but this is a conclusion the data cannot support.
How to Conduct a Pilot Test of a Questionnaire?
Pilot testing a questionnaire checks whether questions are clear, relevant, and produce usable data before deployment at scale.
| Step | Action |
| Define what you’re testing | Decide whether you’re checking wording clarity, question order, response options, completion time, or the validity and reliability of an existing scale. |
| Select a pilot sample | Choose 10–30 people who reflect the target population’s demographics, language level, and familiarity with the topic. A minimum of 10 is often cited as sufficient for basic pre-testing. |
| Administer under realistic conditions | Use the same delivery mode (online, paper, phone, in-person) and setting planned for the main study. |
| Time the completion | Record how long it takes participants to finish, and flag any sections where people slow down, skip items, or appear confused. |
| Collect feedback on each item | Ask participants to flag confusing wording, ambiguous response scales, missing options (e.g., “prefer not to say”), or culturally inappropriate questions. |
| Check data patterns | Look for items with no variation in responses (everyone picks the same option), high rates of “don’t know,” or items left blank. |
| Test reliability if using a scale | Calculate internal consistency (e.g., Cronbach’s alpha) if the questionnaire includes a multi-item scale being adapted or translated. |
| Revise and re-test if needed | Make changes based on findings. If changes are substantial, consider a second small pilot before full deployment. |
What to look for in pilot responses:
- Items consistently skipped or left blank
- Response options that don’t cover real answers (forcing “other”)
- Questions interpreted differently than intended
- Double-barrelled questions (asking two things at once)
- Leading or loaded wording
- Completion time significantly longer than expected
- Technical issues with the survey platform (for online questionnaires)
Techniques for pilot-testing a questionnaire:
- Cognitive interviewing: Ask participants to think aloud as they answer, explaining how they interpreted each question
- Think-aloud protocol: Similar to cognitive interviewing, used to surface comprehension issues in real time
- Debriefing questions: Add a short set of questions at the end asking specifically about clarity, length, and difficulty
- Test-retest: Administer the questionnaire twice to the same small group to check for consistency over time
How to Conduct a Pilot Study for Qualitative Research?
Pilot studies in qualitative research test interview guides, focus group protocols, facilitation approaches, and the overall feasibility of generating rich, usable data.
| Step | Action |
| Develop a draft guide | Create the interview or focus group guide with open-ended questions, probes, and prompts. |
| Recruit a small sample | Select 3–8 participants for interviews, or 1–2 focus groups, who reflect the characteristics of the intended sample. |
| Conduct in realistic conditions | Use the same setting, format (in-person, video, phone), and recording method planned for the main study. |
| Reflect on facilitation | Note where questions felt awkward, where participants seemed confused, and where probes were needed but missing. |
| Review the data generated | Transcribe and review pilot transcripts to check whether the questions produce data relevant to the research aims. |
| Assess practical logistics | Evaluate session length, recording quality, transcription time, and participant comfort. |
| Revise the guide | Remove or reword questions that didn’t generate useful responses; add probes where participants needed more prompting. |
What to Check When Piloting Interviews
- Do questions elicit detailed, reflective answers or short, closed responses?
- Is the question order logical and does it build rapport before moving to sensitive topics?
- Are there unnecessary or redundant questions that can be cut?
- Does the interview run within the planned time?
- Are recording equipment and consent procedures working smoothly?
- Did any questions cause discomfort, confusion, or distress that needs to be addressed?
What to Check When Piloting Focus Groups
- Does the facilitator’s guide allow enough time for group discussion versus individual responses?
- Do participants engage with each other, or does the facilitator have to do most of the talking?
- Are there dominant voices that need to be managed through facilitation technique?
- Does the group size (typically 6–10) work well for the venue and topic?
- Are ground rules (confidentiality, respectful disagreement) clearly communicated and effective?
- Does the topic guide need reordering based on how naturally the conversation flowed?
Pilot Studies in Qualitative vs Quantitative Research
| Aspect | Qualitative Research | Quantitative Research |
| Primary purpose of pilot | Test interview/focus group guides, facilitation approach, and whether questions generate rich, relevant data | Test instrument clarity, completion time, response validity, and recruitment/retention logistics |
| Typical sample size | 3–8 for interviews; 1–2 focus groups | 10–30 participants for questionnaires; 20–30 for intervention-based feasibility pilots |
| What is refined | Topic guide wording, question order, probes, facilitation technique | Questionnaire items, response scales, instrument reliability, protocol procedures |
| How findings are evaluated | Thematic review of transcripts; participant engagement and comfort | Response patterns, completion rates, reliability statistics (e.g., Cronbach’s alpha), feasibility benchmarks |
| Flexibility for changes | High: guides can be substantially reworded between pilot and main study | Moderate: major changes to a validated scale may require re-piloting |
| Role of researcher/facilitator | Central: facilitation skill directly affects data quality, so pilot also tests the researcher’s approach | Minimal: instrument is typically self-administered or follows a fixed script |
| Reporting focus | Whether questions elicited depth, relevance, and natural conversation flow | Whether items were understood, answered consistently, and completed within expected time |
| Statistical analysis | None, analysis is interpretive/thematic | Descriptive only; no inferential statistics or hypothesis testing |
Frequently Asked Questions
1. My supervisor told me to do a pilot; does that alone make it a valid pilot study?
No. A study is a pilot because it is explicitly designed to test feasibility, with clearly stated feasibility objectives and pre-specified progression criteria. Being assigned a small project, having limited funding, or being a student are not valid reasons to call a study a pilot. Without a feasibility-oriented design, the findings will have limited utility, and labelling the work a pilot does not change that.
2. Can I include pilot participants in my main study?
It depends on the design. In an internal pilot, data from pilot participants can be retained in the final analysis, but only if no major protocol changes were required. In an external pilot, pilot participants’ data should not be included in the main study because they have been exposed to a version of the intervention or instruments that may differ from the final protocol. Including them risks contamination in that they may respond differently from participants who have not been previously exposed.
3. How many participants do I actually need; my supervisor says 30 but I planned on 10?
Both numbers can be defensible depending on the study type and objectives. For simple questionnaire pre-testing, 10 is often adequate. For intervention-based feasibility studies, 20–30 is a widely cited range. The right number is determined by your feasibility benchmarks, not by a universal rule. Document your reasoning explicitly in the pilot protocol, citing what number is sufficient to evaluate your specific feasibility goals.
4. Can I publish my pilot study results?
Yes, and you are encouraged to do so. Pilot findings, including failures, are valuable to other researchers planning similar work. The key is to frame findings around feasibility outcomes, not statistical significance. Report your pre-specified benchmarks, whether they were met, and exactly how the pilot changed (or confirmed) your main study design. Many journals that publish clinical and health research now actively accept pilot and feasibility study reports.
5. Where do I write up my pilot study in a dissertation: methods or results?
Most examiners and supervisors recommend including it in the methodology chapter of your dissertation, specifically within the section on instrumentation or study design. The key requirement is that pilot data are kept clearly separate from main study results. If the pilot led to changes in your instruments or procedures, explain those changes and their rationale in the methodology section. Do not mix pilot findings into your main results chapter.
6. Is it ever acceptable to skip the pilot study?
In some circumstances, yes. If the methods, instruments, and procedures have been extensively validated in prior studies in the same population, or if the study replicates an established protocol with no modifications, a pilot may add little value. However, the decision to skip should be explicitly justified in the study protocol. For novel interventions, new populations, or untested instruments, skipping the pilot is a significant methodological risk.
7. Can a pilot study be used to justify that an intervention is safe?
No. Because of the small sample sizes involved, a pilot study can only detect safety signals in extreme cases, for example, repeated serious adverse events. If no adverse events occur in a pilot of 20 participants, this does not mean the intervention is safe. It means only that no events were observed in that small group. Formal safety and tolerability assessment requires a study that is specifically powered and designed for that purpose.
8. What is the difference between a pilot study and a feasibility study?
The terms are often used interchangeably, but some methodologists distinguish between them. Under the NIHR framework, ‘feasibility’ is the broader umbrella term for all preliminary work, while ‘pilot’ refers specifically to a study that closely resembles the main trial in design (e.g., one that includes a control group or randomization). In practice, the most important thing is to clearly state your study’s purpose and objectives. Whether you call it a pilot or a feasibility study, the design should be driven by what you need to learn before running the main study.
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This article was originally published on March 13, 2025, and updated on June 12, 2026.
