The value of randomization and control in clinical trials.

This paper examines the two principal justifications that have been offered for the standard conditions that clinical trials be randomized and controlled, with the conclusion that, strictly speaking, neither justification is valid. It is argued, on the other hand, that a Bayesian analysis of clinical trials affords a valid, intuitively plausible rationale for selective controls, and marks out a more limited role for randomization than it is generally accorded. The feasibility of retrospective trials is then considered in the light of these conclusions.