Restricted Randomization in Practice

This chapter outlines the basic steps in determining an appropriate randomization procedure to use, generating the randomization sequence, and implementing the randomization in the clinical trial. It reviews important characteristics of the restricted randomization procedures. The basic issue is a trade-off between the desire to promote or guarantee balance in the numbers of treatment assignments versus the susceptibility to either selection bias or accidental covariate imbalances. The restricted randomization procedures have only been compared with respect to an individual criterion separately. Trade-off plots are useful in comparing restricted randomization procedures, and they can facilitate the appropriate selection of procedures for different criteria. While each trial has its own unique considerations, and some criteria may be more important than others, there are some interesting observations that can be made based on the limited investigations the authors have conducted.