Proschan M A, Hunsberger S A
Office of Biostatistics Research, National Heart, Lung, and Blood Institute, Bethesda, Maryland 20892, USA.
Biometrics. 1995 Dec;51(4):1315-24.
We propose a flexible method of extending a study based on conditional power. The possibility for extension when the p value at the planned end is small but not statistically significant is built in to the design of the study. The significance of the treatment difference at the planned end is used to determine the number of additional observations needed and the critical value necessary for use after accruing those additional observations. It may therefore be thought of as a two-stage procedure. Even though the observed treatment difference at stage 1 is used to make decisions, the Type I error rate is protected.
我们提出了一种基于条件功效来扩展研究的灵活方法。在研究设计中纳入了在计划结束时p值较小但无统计学显著性时进行扩展的可能性。利用计划结束时治疗差异的显著性来确定所需的额外观察次数以及积累这些额外观察值后使用的临界值。因此，它可被视为一个两阶段程序。尽管在第一阶段观察到的治疗差异用于做出决策，但I型错误率仍得到了控制。
