Table of Contents
International Journal of Quality, Statistics, and Reliability
Volume 2010 (2010), Article ID 942184, 4 pages
http://dx.doi.org/10.1155/2010/942184
Research Article

Power Loss of Stratified Log-Rank Test in Homogeneous Samples

Department of Biostatistics and Computational Biology, University of Rochester, Rochester, NY 14642, USA

Received 25 September 2009; Accepted 7 February 2010

Academic Editor: Myong K. Jeong

Copyright © 2010 Changyong Feng et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We study the loss of power of the stratified log-rank test (SLRT) compared to the unstratified log-rank test (ULRT) in the case of a large number of strata with relatively a small number of stratum sizes in terms of the asymptotic distributions of test statistics under local alternatives. The SLRT tends to lose information due to overstratification. It is better to test the homogeneity among strata before using the stratified log-rank test.