# Survival analysis (Kaplan-Meier curves, log-rank test etc.)

Survival analysis for two groups (treatments) with provision for right censoring. The module draws Kaplan-Meier survival curves for the two groups and computes three different tests for equivalence. The program expects four columns. The first column contains times to failure (death) or censoring (failure not observed up to and including the given time) for the first group, the second column indicates failure (1) or censoring (0) for the corresponding individuals. The last two columns contain data for the second group. Failure times must be larger than zero.

The program also accepts only one treatment (given in two columns), or more than two treatments in consecutive pairs of columns, plotting one or multiple Kaplan-Meier curves. The statistical tests are only comparing the first two groups, however.

The Kaplan-Meier curves and the log-rank, Wilcoxon and Tarone-Ware tests are computed according to Kleinbaum & Klein (2005).

Average time to failure includes the censored data. Average hazard is number of failures divided by sum of times to failure or censorship.

For further mathematical details see the Past manual.

This module is not strictly necessary for survival analysis without right censoring – the Mann-Whitney test may be sufficient for this simpler case.

**Missing data**: Data points with missing value in one or both columns are disregarded.

#### Reference

Kleinbaum, D.G. & Klein, M. 2005. *Survival analysis: a self-learning text*. Springer.