# 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.