User Guide

101
Cox Regression Analysis
 Select one or more covariates. To include interaction terms, select all of the variables
involved in the interaction and then select
>a*b>.
Optionally, you can compute separate models for different groups by defining a
strata variable.
Cox Regression Define Categorical Variables
Figure 11-2
Cox Regression Define Categorical Covariates dialog box
You can specify details of how the Cox Regression procedure will handle
categorical variables.
Covariates. Lists all of the covariates specified in the main dialog box, either by
themselves or as part of an interaction, in any layer. If some of these are string variables
or are categorical, you can use them only as categorical covariates.
Categorical Covariates. Lists variables identified as categorical. Each variable includes
a notation in parentheses indicating the contrast coding to be used. String variables
(denoted by the symbol < following their names) are already present in the Categorical
Covariates list. Select any other categorical covariates from the Covariates list and
move them into the Categorical Covariates list.
Change Contrast. Allows you to change the contrast method. Available contrast
methods are:
 Indicator. Contrasts indicate the presence or absence of category membership. The
reference category is represented in the contrast matrix as a row of zeros.