JSM 2005 - Toronto

Abstract #302969

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Legend: = Applied Session, = Theme Session, = Presenter
Activity Number: 51
Type: Invited
Date/Time: Sunday, August 7, 2005 : 4:00 PM to 5:50 PM
Sponsor: Biometrics Section
Abstract - #302969
Title: Sample-Size Formula for Clustered Survival Data Using Weighted Log-rank Statistics
Author(s): Ronald Gangnon*+ and Michael Kosorok
Companies: University of Wisconsin, Madison and University of Wisconsin, Madison
Address: 207 WARF Office Building, Madison, WI, 53726,
Keywords: Clustered data ; Log-rank statistic ; Local alternatives ; Martingale residuals ; Paired data ; Proportional hazards
Abstract:

We present a simple sample-size formula for weighted log-rank statistics applied to clustered survival data with variable cluster sizes and arbitrary treatment assignments within clusters. This formula is based on the asymptotic normality of weighted log-rank statistics under certain local alternatives in the clustered data context. We also provide consistent variance estimators. The derived sample-size formula reduces to Schoenfeld's (1983) formula for cases of no clustering or independence within clusters. Simulation results verify control of the Type I error and accuracy of the sample-size formula. Use of the sample-size formula in an event-driven clinical trial design is illustrated using data from the Early Treatment Diabetic Retinopathy Study.


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Revised March 2005