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:

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Specify the Input SAS Data Set.

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

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

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Examine the list of available variables.

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

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