Group sequential methods for clinical trials with a one-sided hypothesis

SUMMARY Pocock (1977) has recently proposed group sequential methods for sequential analysis of clinical trials. However, these methods are intended to test a null hypothesis against a twosided alternative, and many trials of a new therapy against a standard have one-sided alternatives. Continuation of the trial to determine whether the new therapy is actually inferior to the standard therapy may be inappropriate or even unethical. In the present paper, three possible modifications of the group sequential method for sequential monitoring of clinical trials testing a one-sided hypothesis are considered.