| Abstract: | Since the treatment effect of an experimental drug is generally not known at the onset of a clinical trial, it may be wise to allow for an adjustment in the sample size after an interim analysis of the unblinded data. Using a particular adaptive test statistic, a procedure is demonstrated for finding the optimal design. Both the timing of the interim analysis and the way the sample size is adjusted can influence the power of the resulting procedure. It is possible to have smaller average sample size using the adaptive test statistic, even if the initial estimate of the treatment effect is wrong, compared to the sample size needed using a standard test statistic without an interim look and assuming a correct initial estimate of the effect. Copyright © 2002 John Wiley & Sons, Ltd. |
