Frank Miller: Statistical Aspects of Adaptive Designs in Clinical Studies

Adaptive designs became popular in recent years in the context of clinical studies. Mid-term during an ongoing study, changes to the design can be conducted based on the data collected until then. This design adaptation offers the opportunity to handle uncertainties in the planning phase of the study. However, if data dependent changes are done during a study, statistical inference is more complicated. Unexpected effects on the properties of estimators and tests can be introduced.

We consider a sample size re-estimation design which is an example of a specific adaptive design. We explain for this design why a bias for an estimator and a test occurs and how one can correct for it.