Spiegelhalter D J, Freedman L S, Blackburn P R
Control Clin Trials. 1986 Mar;7(1):8-17. doi: 10.1016/0197-2456(86)90003-6.
At an interim point in a clinical trial, trial organisers may wish to use the data on the initial series of patients to judge the likely consequences of further patient accrual. Halperin and colleagues (Controlled Clin Trials 3:311-323, 1982) have suggested calculating the power of a continued trial, conditional on the data observed so far and the null and alternative hypothesis specified at the start of the trial. Here we argue that this idea should be extended to obtain the predictive power of the trial, derived by averaging the conditional power with respect to the current belief about the unknown parameters. Although numerical methods are generally required for evaluating the necessary integrals, the results may be presented graphically and enable the statistician to answer the question: "With the data so far, what is the chance that the trial will end up showing a conclusive result?"
在一项临床试验的中间阶段，试验组织者可能希望利用最初一系列患者的数据来判断进一步纳入患者可能产生的结果。哈尔珀林及其同事（《对照临床试验》3:311 - 323，1982年）建议根据目前观察到的数据以及试验开始时指定的原假设和备择假设，计算继续试验的检验效能。在此我们认为，这一理念应加以扩展，以获得试验的预测效能，即通过对关于未知参数的当前信念的条件效能进行平均得出。虽然通常需要数值方法来评估必要的积分，但结果可以以图形方式呈现，使统计学家能够回答以下问题：“根据目前的数据，试验最终得出决定性结果的可能性有多大？”
