# Example 7.42: Testing the proportionality assumption

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In addition to the non-parametric tools discussed in recent entries, it’s common to use proportional hazards regression, (section 4.3.1) also called Cox regression, in evaluating survival data.It’s important in such models to test the proportionality assumption. Below, we demonstrate doing this for a simple model from the HELP data, available at the book web site. Our results below draw on this
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