# Kaplan-Meier Compare Factor Levels

You can request statistics to test the equality of the survival distributions for the different levels of the factor. Available statistics are log rank, Breslow, and Tarone-Ware. Select one of the alternatives to specify the comparisons to be made: pooled over strata, for each stratum, pairwise over strata, or pairwise for each stratum.

**Linear trend for factor levels.** Allows you to test for a linear trend across levels of the
factor. This option is available only for overall (rather than pairwise) comparisons of factor
levels.

- Log rank. A test for comparing the equality of survival distributions. All time points are weighted equally in this test.
- Breslow. A test for comparing the equality of survival distributions. Time points are weighted by the number of cases at risk at each time point.
- Tarone-Ware. A test for comparing the equality of survival distributions. Time points are weighted by the square root of the number of cases at risk at each time point.
- Pooled over strata. Compares all factor levels in a single test to test the equality of survival curves.
- Pairwise over strata. Compares each distinct pair of factor levels. Pairwise trend tests are not available.
- For each stratum. Performs a separate test of equality of all factor levels for each stratum. If you do not have a stratification variable, the tests are not performed.
- Pairwise for each stratum. Compares each distinct pair of factor levels for each stratum. Pairwise trend tests are not available. If you do not have a stratification variable, the tests are not performed.

Comparing Factor Levels

This feature requires SPSS® Statistics Standard Edition or the Advanced Statistics Option.

- From the menus choose:
- In the Kaplan-Meier dialog box, select a factor variable and then click Compare Factor.