Comparison of a Two-Stage and Three-Stage Interim-Analysis Procedure

A statistical model for combining p values from multiple tests of significance is used to define rejection and acceptance regions for two-stage and three-stage sampling plans. Type I error rates, power, frequencies of early termination decisions, and expected sample sizes are compared. Both the two-stage and three-stage procedures provide appropriate protection against Type I errors. The two-stage sampling plan with its single interim analysis entails minimal loss in power and provides substantial reduction in expected sample size as compared with a conventional single end-of-study test of significance for which power is in the adequate range. The three-stage sampling plan with its two interim analyses introduces somewhat greater reduction in power, but it compensates with greater reduction in expected sample size. Either interim-analysis strategy is more efficient than a single end-of-study analysis in terms of power per unit of sample size

Clinical trial · Interim · Interim analysis · Power (physics · Reduction (mathematics · Sample (material · Sample size determination · Sampling (signal processing · Stage (stratigraphy · Statistical power · Statistics · Telecommunications · Type I and type II errors · Chemistry · Computer Science · Mathematics · Medicine · Optimal Experimental Design Methods · Statistical Methods and Bayesian Inference · Statistical Methods in Clinical Trials