JSM 2011 Online Program

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Abstract Details

Activity Number: 34
Type: Contributed
Date/Time: Sunday, July 31, 2011 : 2:00 PM to 3:50 PM
Sponsor: Biopharmaceutical Section
Abstract - #302694
Title: Mean-Variance Relationships in Longitudinal Group Sequential Trials
Author(s): Abigail Shoben*+ and Scott Emerson
Companies: The Ohio State University and University of Washington
Address: B-112, Starling Loving Hall, Columbus, OH, 43210,
Keywords: Sequential analysis ; Longitudinal data ; Mean-variance relationship
Abstract:

In group sequential trials, interim analyses are performed for ethical and financial considerations. In order to perform such analyses, estimates of the statistical information at the time of the interim analysis relative to the amount of statistical information at the end of the trial are needed. We consider potential difficulties due to mean-variance relationships in a longitudinal setting, such as a changing Poisson rate over time. The amount of heteroscedasticity between measurements at different times affects the information growth. Thus the information growth will be different for different alternatives. We find that this relationship can cause difficulties in extreme settings, but that adjusting for the observed information growth at the end of the study is sufficient to maintain type I error rates in most realistic circumstances. An additional concern is deviation from the assumed independent increment structure for the covariance of the interim and final statistics. We give examples in which the lack of independent increments may cause departures from the nominal type I error rate, but show that in most circumstances existing group sequential methodology can be used.


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