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Doctoral Dissertation Announcement
Candidate: Ruvie Lou Maria C. Martinez
Doctor of Philosophy
Title: Diagnostics for Choosing Between Log-rank and Wilcoxon Tests
Dr. Joshua D. Naranjo, Chair
Dr. Michael R. Stoline
Dr. Magdalena Niewiadomska-Bugaj
Dr. Douglas N. Homnick
Date: Friday, September 21, 2007 10:00 a.m.- 12:00 p.m.
6625 Everett Tower
Two commonly used tests for comparison of survival curves are the generalized Wilcoxon procedure of Gehan (1965) and Breslow (1970) and the Log-rank test proposed by Mantel (1966) and Cox (1972). In applications, the Log-rank test is used after checking for validity of the proportional hazards (PH) assumption, with Wilcoxon being the fallback method when the PH assumption fails.
However, the relative performance of the two procedures depends not just on the PH assumption but also on the pattern of differences between the two curves. The crucial factor is whether the differences tend to occur early or late in time. We propose diagnostics to measure early-or-late differences between two survival curves. Simulations show that a pretest based on either diagnostic will help the user choose the more efficient test under various patterns of treatment differences.