PROC PHREG Modeling Options

Enter SAS PROC PHREG MODEL statement options in this field to override default parameters.

You can specify any PROC PHREG MODEL option using the following syntax:

(t1, t2) <*censor ( list )> = effects </options>

where:

•	(t1, t2) are the failure time variables,

•	<censor (list)> is an optional censoring variable,

•	effects </options> are the explanatory effects, including covariates, main effects, interactions, and nested effects.

Examples of commonly used PROC PHREG MODEL options are listed in the following table:

Option	Definition
ALPHA=n	This option sets the significance level used for the confidence limits for the hazard ratios. The value must be between 0 and 1. The default is the value of the ALPHA= option in the PROC PHREG statement, or 0.05 if that option is not specified. This option has no effect unless the RISKLIMITS option is specified
BEST=n	This option is used exclusively with the SCORE model selection method. The BEST=n option specifies that n models with the highest-score chi-square statistics are to be displayed for each model size. • If the option is omitted and there are no more than 10 explanatory variables, then all possible models are listed for each model size. • If the option is omitted and there are more than 10 explanatory variables, then the number of models selected for each model size is, at most, equal to the number of explanatory variables listed in the MODEL statement.
MAXSTEP=n	This option specifies the maximum number of times the explanatory variables can move in and out of the model before the STEPWISE model-building process ends. The default value for n is twice the number of explanatory variables in the MODEL statement. The option has no effect for other model selection methods.
RISKLIMITS<=keyword>	This option produces confidence intervals for hazard ratios of main effects not involved in interactions or nestings. Computation of these confidence intervals is based on the profile likelihood or based on individual Wald tests. The confidence coefficient can be specified with the ALPHA= option. You can specify one of the following keywords: • PL - requests profile-likelihood confidence limits • WALD - requests confidence limits based on the Wald tests, and • BOTH- request both profile-likelihood and Wald confidence limits

To Specify One or More PROC PHREG MODEL Options:

Type specific PROC PHREG MODEL options in the PROC PHREG MODEL Options field.

For example, specify HIERARCHY=MULTIPLE to allow multiple related effects to enter or leave the model at the same time as shown below:

For Additional Information

Refer to the SAS PROC PHREG MODEL Statement documentation more information.