Design and Analysis of Group Sequential Tests Based on the Type I Error Spending Rate Function
扩展了Lan & DeMets的方法，生成临床试验中对称或非对称的双侧边界，并探讨了设计方面，包括达到预期功效所需的最大样本量和预期停止时间。
Lan & DeMets (1983) devised a method of constructing discrete group sequential boundaries by using the type I error spending rate function. It is extended so as to generate asymmetric as well as symmetric two-sided boundaries for clinical trials. The design aspect of this procedure is explored in terms of the maximum sample size needed to achieve a desired level of power and the expected stopping times under both null and alternative hypotheses. Finally, these properties are employed in search of appropriate type I error spending rate functions for differing situations.