Using Pilot Study Information to Increase Efficiency in Clinical Trials

Abstract

A pilot study is often necessary to determine the sample size required for a clinical trial. Due to differences in sampling environments, the pilot data are usually discarded after sample size calculation. This paper tries to use the pilot information to modify the subsequent testing procedure when the t- test or a regression model is used to compare two treatments. The new test maintains the required significance level reqardless the similarity of the pilot and the target populations, but increases the power when the two are similar. The test is constructed based on the posterior distribution of the parameters from the pilot data information, but its properties are investigated from a frequentist's viewpoint. Due to the small likelihood of an irrelevant pilot population, the new approach is a viable alternative to the current practice.