A brief overview of pilot studies and their sample size justification

Pilot studies, when properly designed and implemented, are an important tool that provide critical information for the development and potential success of a subsequent, larger trial. In fact, these small-scale studies are commonly used to assess the feasibility of whether a larger trial should be initiated. A popular investigator question is whether a pilot study requires a formal statistical power calculation. In general, the answer is "no"; however, the sample size needs to be justified on the basis of the goal of the pilot study.