Choosing Interim Sample Sizes in Group Sequential Designs

Minimum Sample Sizes with Rare Events in Stratified Designs

There are many statistical issues in using stratified sampling for rare events. They include designing to ensure enough of the rare events are found in each stratum, achieving adequate accuracy of the estimates and their variance, and meeting the normality assumptions for confidence interval construction. When sampling to estimate sales and use tax, a large population is sampled to find a rare ...

Asymptotic Optimal Sample Sizes for Discovering a Promising Treatment in Phase II Group Sequential Clinical Trials

We propose an asymptotic optimal procedure for determining the per-study sample size of a series of Phase II clinical studies. The sequence of studies seeks to discover an active treatment among a sequence of treatments under evaluation. Each phase II study proceeds in r stages with r=1, 2, or 3. Our result serves two practical purposes. First, it yields asymptotic optimal sample sizes. Second,...

Efficient group sequential designs when there are several effect sizes under consideration.

We consider the construction of efficient group sequential designs where the goal is a low expected sample size not only at the null hypothesis and the alternative (taken to be the minimal clinically meaningful effect size), but also at more optimistic anticipated effect sizes. Pre-specified Type I error rate and power requirements can be achieved both by standard group sequential tests and by ...

Issues in Group Sequential/Adaptive Designs

In recent years, there has been great interest in the use of adaptive features in clinical trials (i.e., changes in design or analyses guided by examination of the accumulated data at an interim point in the trial) that may make the studies more efficient (e.g., shorter duration, fewer patients). Many statistical methods have been developed to maintain the validity of study results when adaptiv...

Group sequential designs for clinical trials.