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Type I error and power in trials with one interim futility analysis
Author(s) -
Chang William H.,
ChuangStein Christy
Publication year - 2004
Publication title -
pharmaceutical statistics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.421
H-Index - 38
eISSN - 1539-1612
pISSN - 1539-1604
DOI - 10.1002/pst.93
Subject(s) - type i and type ii errors , interim , interim analysis , commit , sample size determination , power analysis , reduction (mathematics) , statistics , nominal level , set (abstract data type) , computer science , statistical power , power (physics) , error analysis , reliability engineering , econometrics , clinical trial , medicine , confidence interval , mathematics , algorithm , engineering , physics , geometry , archaeology , quantum mechanics , database , cryptography , history , programming language
Futility analysis reduces the opportunity to commit Type I error. For a superiority study testing a two‐sided hypothesis, an interim futility analysis can substantially reduce the overall Type I error while keeping the overall power relatively intact. In this paper, we quantify the extent of the reduction for both one‐sided and two‐sided futility analysis. We argue that, because of the reduction, we should be allowed to set the significance level for the final analysis at a level higher than the allowable Type I error rate for the study. We propose a method to find the significance level for the final analysis. We illustrate the proposed methodology and show that a design employing a futility analysis can reduce the sample size, and therefore reduce the exposure of patients to unnecessary risk and lower the cost of a clinical trial. Copyright © 2004 John Wiley & Sons, Ltd.