# Predictors (Complex Samples Cox Regression)

The Predictors tab allows you to specify the factors and covariates used to build model effects.

**Factors.** Factors are categorical predictors; they can
be numeric or string.

**Covariates.** Covariates are scale predictors; they must
be numeric.

**Time-Dependent Predictors.** There are certain situations
in which the proportional hazards assumption does not hold. That is,
hazard ratios change across time; the values of one (or more) of your
predictors are different at different time points. In such cases,
you need to specify time-dependent predictors. See the topic Define Time-Dependent Predictor (Complex Samples Cox Regression) for more information. Time-dependent predictors
can be selected as factors or covariates.

How To Specify Predictors

This feature requires the Complex Samples option.

- From the menus choose:
- Select a plan file. Optionally, select a custom joint probabilities file and then click Continue.
- In the Complex Samples Cox Regression dialog box, click the Predictors tab.