Abstract #300260

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JSM 2002 Abstract #300260
Activity Number: 129
Type: Invited
Date/Time: Monday, August 12, 2002 : 2:00 PM to 3:50 PM
Sponsor: Biopharmaceutical Section*
Abstract - #300260
Title: Flexible Sample Size: Still No Free Lunch!
Author(s): Christopher Jennison*+
Affiliation(s): University of Bath
Address: , Bath, International, BA2 7AY, England
Keywords: Adaptive Design ; Group Sequential Test ; Clinical Trial ; Error spending ; Variance Spending
Abstract:

The practice of re-designing a study in response to an estimate of the likely effect size goes against the traditional advice that power should be set before embarking on a study. Recent work has shown that sample size can be altered in order to increase power while still preserving the original Type I error rate. But are there hidden inefficiencies in this approach?

I shall examine the overall effectiveness of recent proposals, integrating over the distribution of estimates of treatment effect used to re-calculate sample size. My conclusion is that it pays to address power requirements properly before starting a study--the flexibility of adaptive methods can be at the price of substantial increases in expected sample size.

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Revised March 2002