# Stratifying a proportional hazards model by a category column

In a proportional hazards model, if groups of observations are expected to have different underlying hazard rates, the model can be stratified using a category column. A common example is stratifying medical data by sex, so that a separate hazard rate is estimated for males and females.

To stratify the model using a category column:

1. In the Model view, ensure that Proportional Hazards is selected from the Model pop-up button
2. Click the Configure button to the right of the Model pop-up button
3. Check the box labeled Stratify by and select a category column from the pop-up button

For purposes of prediction, individual strata may be selected in the Predict view using the pop-up button below the survival curve in the bottom-left corner.

See also:

- Treating records as censored in a proportional hazards models
- Defining default outcome values in a proportional hazards models
- Defining the cause of failure in a proportional hazards models
- About proportional hazards models

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