Pilot Study vs. Feasibility Study: What’s the Difference?

Are Pilot Studies and Feasibility Studies the Same Thing?

The terms pilot study and feasibility study are often used together, and sometimes interchangeably. That can make the distinction seem more complicated than it needs to be. A researcher may describe a small preliminary project as a pilot because it occurs before a larger study, while another researcher might call similar work a feasibility study.

There is genuine variation in terminology across disciplines and research traditions. However, an influential methodological framework developed for studies preparing for randomized controlled trials offers a useful distinction: feasibility is the broader concept, concerned with whether and how a future study can be done, while a pilot study is a particular type of feasibility work in which part or all of the future study is conducted on a smaller scale.

The distinction matters because the label should follow the purpose and design of the preliminary research. Calling something a pilot study does not automatically make its objectives appropriate, just as calling something a feasibility study does not explain what was actually assessed.

Feasibility Is the Broader Question; Piloting Is One Way to Investigate It

How Pilot and Feasibility Studies Differ

Feasibility Begins With the Question: Can This Study Be Done?

Feasibility concerns whether something can work in practice. In research conducted in preparation for a future study, the relevant uncertainties might involve recruitment, retention, intervention delivery, acceptability, participant burden, randomization, data collection, staffing, resources, follow-up, or other operational features.

A feasibility study is therefore defined principally by the questions it investigates. Researchers might ask whether enough eligible participants can be recruited, whether participants will accept a proposed intervention, whether study sites can implement the protocol, or whether follow-up assessments can be completed at an acceptable rate.

Importantly, investigating feasibility does not necessarily require reproducing the entire future study. Researchers can use quantitative methods, qualitative methods, mixed methods, simulations, observations, interviews, or other approaches appropriate to the uncertainty being examined.

This is why the question what a feasibility study should actually tell you is more useful than simply asking whether a preliminary project is large enough to deserve the label.

A Pilot Study Runs the Future Study, or Part of It, on a Smaller Scale

A pilot study is more closely tied to the procedures intended for the future study. It tests those procedures by implementing them on a smaller scale.

For example, researchers preparing a randomized trial might pilot the planned sequence of recruitment, consent, baseline assessment, randomization, intervention delivery, and follow-up. The objective is not primarily to determine whether the intervention is effective. It is to learn whether the intended study processes can operate together and what may need modification before the definitive study.

This explains why simply conducting a small study does not make it a pilot. A small exploratory or underpowered study does not become a pilot merely because researchers hope to conduct a larger one later. The defining feature is its preparatory relationship to the future study and its objectives concerning that future study.

The Relationship Is Better Understood as Overlap, Not Opposition

It is tempting to treat “pilot study” and “feasibility study” as two mutually exclusive research designs. The relationship is more nuanced.

In the conceptual framework proposed by Eldridge and colleagues for research preparing for randomized controlled trials, feasibility is the overarching concept. Pilot studies fall within that broader domain because they investigate feasibility by implementing the future study, or part of it, on a smaller scale.

Under this framework, the useful question is not “pilot or feasibility?” as though the categories never overlap. Instead ask what uncertainty needs to be resolved and whether answering it requires trying the future study procedures in practice.

A Feasibility Study Does Not Have to Look Like the Main Study

Suppose a research team is uncertain whether a target population would accept a proposed intervention. Interviews or focus groups might provide the information needed to investigate that uncertainty. Such work could contribute directly to feasibility assessment without reproducing the eventual trial.

Similarly, researchers might investigate the availability of eligible participants across several sites, assess whether required equipment is available, or examine whether institutions are willing to participate. These questions can determine whether a future study is possible without requiring a miniature version of the complete study.

A pilot becomes particularly useful when the uncertainty concerns how study procedures function when implemented together. If recruitment appears feasible separately, an intervention appears acceptable separately, and an instrument performs adequately separately, researchers may still need to know whether the complete sequence works under realistic study conditions.

The Main Outcome Is Usually About the Future Study

Another important distinction separates preliminary feasibility work from a definitive study. The central questions of a pilot or feasibility study should generally concern the future research process rather than provide a definitive answer to the substantive research question intended for the main study.

Relevant outcomes might include recruitment rates, retention, completion of assessments, adherence to procedures, acceptability, fidelity, missing-data patterns, or the practicality of particular study processes. Which outcomes matter depends on the uncertainties identified before the study begins.

This also means that researchers should be cautious about using a small pilot to test whether an intervention “works.” Pilot estimates of substantive effects may be highly imprecise, and statistical significance or non-significance in a small preliminary sample can be misleading. Understanding what should not be concluded from a pilot study is therefore part of designing one responsibly.

Internal and External Pilots Add Another Distinction

A pilot may be external or internal to the main study. In an external pilot, the preliminary study is conducted separately and its data ordinarily remain separate from the definitive study. This arrangement allows researchers to make substantial changes before the main study begins.

An internal pilot forms an initial phase of the main study. Provided prespecified conditions are met and changes do not undermine the integrity of the design, participants or data from that phase may contribute to the final study.

This distinction has important methodological implications. Researchers should not assume after seeing pilot results that preliminary participants can simply be transferred into the main dataset. Whether pilot participants or data can be included in the main study depends on how the pilot was designed and what changed afterward.

Terminology Varies, So Describe What You Actually Did

Definitions of pilot and feasibility studies have historically varied, and usage remains inconsistent across research communities. Some sources use “pilot” broadly for almost any preliminary investigation. Others distinguish pilot work more narrowly from other feasibility research.

For researchers, this variation makes transparent reporting especially important. A title such as “pilot study” should not carry the burden of explaining the design. State the preparatory objectives, the uncertainties being examined, the methods used, the criteria for interpreting the findings, and how the results will influence the future study.

How the Same Research Program Could Use Feasibility Work and a Pilot

Both stages address feasibility. The distinction lies in how they investigate it. The first examines specific feasibility uncertainties without running the future study as a miniature version. The pilot subsequently tests how intended study procedures operate when put into practice together.

Common Misunderstandings About Pilot and Feasibility Studies

Should You Call Your Preliminary Research a Pilot or a Feasibility Study?

Choose the design from the question you need answered, then choose terminology that accurately describes the work. Starting with the label can encourage researchers to force different preliminary objectives into a single familiar category.

Once you have identified the appropriate approach, make the objectives operational. Instead of saying that the study will “assess feasibility,” specify what will be assessed and how. Recruitment feasibility, intervention acceptability, follow-up completion, procedural fidelity, and data completeness are different questions and may require different methods and criteria.

If you are still deciding whether preliminary work is warranted at all, consider whether your main research actually needs a pilot or feasibility study before designing one by default.

Before Calling Your Study a Pilot or Feasibility Study, Check

Frequently Asked Questions About Pilot and Feasibility Studies

The Difference Is About Purpose and How Feasibility Is Investigated

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