Testing secondary hypotheses following sequential clinical trials

Sequential monitoring in a clinical trial poses difficulty in hypotheses te sting on secondary endpoints after the trial is terminated. The conventiona l likelihood-based testing procedure that ignores the sequential monitoring inflates Type I error and undermines power. In this article, we show that the power of the conventional testing procedure can be substantially improv ed while the Type I error is controlled. Thr method is illustrated with a r eal clinical trial.