Strata Variables

The Strata Variables can be selected to perform a stratified analysis when the trait is binary or survival. In a stratified analysis for a binary trait , separate intercepts are fit for each stratum, but a single estimate is obtained for each model effect conditional on the intercepts. Stratified survival analysis involves fitting a separate baseline hazard function for each stratum but again calculating a single set of effect estimates.

A censor variable must be selected when performing analysis of a survival trait. This variable indicates which observations have been censored - often, this is an indicator of whether a patient is living at the end of a study.

To Specify One or More Strata Variables:

Specify the Input SAS Data Set .

All of the variables in the specified data set are displayed in the Available Variables field.

Make sure that either Binary or Survival is selected as the Type of Tests to Perform or Type of Trait (whichever is available).

Examine the list of available variables.

Highlight the desired variable(s). Left-click a single variable, or hold down Ctrl while left-clicking multiple variables.

Click to add the highlighted variable(s) to the Strata Variables field.