Strata Variables

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 Trait .

Examine the list of available variables.

Highlight the desired variable(s). To highlight multiple variables, hold down Ctrl while left-clicking.

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