ABSTRACT
Statistical issues in conducting randomized trials include the choice of a sample size, whether to stop a trial early, and the appropriate analysis and interpretation of the trial results. At each of these stages, evidence external to the trial is useful, but generally such evidence is introduced in an unstructured and informal manner. We argue that a Bayesian approach allows a formal basis for using external evidence and in addition provides a rational way for dealing with issues such as the ethics of randomization, trials to show treatment equivalence, the monitoring of accumulating data, and the prediction of the consequences of continuing a study. The motivation for using this methodology is practical rather than ideological.
