# Chapter 3 The Cox Proportional Hazards Model

This Chapter describes the Cox Proportional Hazards model, a very popular statistical model used for analyzing survival data.

As we seen before, the survival function is the probability that the time-to-event will be greater than some specified time and this probability depends on:

the

**underlying hazard function**(how the risk of occurs the event per unit time changes over time at baseline covariates)the

**effect parameters**(how the hazard varies in response to the covariates)

We are going to use the Cox proportional hazards model to determine the effect of the covariates on survival.