non-parametric test log-rank test Mantel–Cox test https://en.wikipedia.org/wiki/Log-rank_test KS test log-rank analysis HL, QL, YH A non-parametric test that compares the survival distributions of two samples, and iis appropriate to use when the data are right skewed and censored (technically, the censoring must be non-informative). It is widely used in clinical trials to establish the efficacy of a new treatment in comparison with a control treatment when the measurement is the time to event (such as the time from initial treatment to a heart attack).