Pharmaceutical Statistics Using SAS

9.1. Introduction

Randomization, an allocation of subjects to treatment regimens using a random element, is an essential component of clinical trials. Randomization promotes comparability of the treatment groups with respect to known as well as unknown covariates and thus reduces the chance for bias in the evaluation of the treatment effect. It can also serve as a basis for a randomization approach to inference (Rosenberger and Lachin, 2002).

Several types of bias are considered in the context of randomization. Selection bias occurs in an unmasked (unblinded) trial when the investigator, either consciously or otherwise, uses knowledge of the upcoming treatment assignment to help decide whom to enroll (Blackwell and Hodges, 1957). Observer bias ...