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Statistical Advisor, How To Compare Survival / Failure Times

Use SURVIVAL ANALYSIS. This chapter describes several tests for comparing survival/failure times in two or more groups. These tests are applicable to censored or uncensored data sets.

SURVIVAL ANALYSIS contains five different (mostly nonparametric) tests for censored data: Gehan's generalized Wilcoxon test, the Cox-Mantel test, the Cox F-test, the log-rank test, and Peto and Peto's generalized Wilcoxon test. A nonparametric test for the comparison of multiple groups is also available.

A data set is said to be 'censored' if some observations are incomplete, but not missing. For example, in industrial reliability testing, a part or product may not fail (break) within the time span covered by a study. However, we do not know how long it will function properly thereafter, and thus, that observation is 'censored.' If your data set contains no censored data points, you can also use the tests for comparing groups or samples discussed in NONPARAMETRICS AND DISTRIBUTIONS.