Survival Curves

In the two previous chapters, we have studied series of events occurring to one or more units (mines, a hospital, voters, …) observed over time. In Chapter 2, each event resulted in a possible switch from one of a relatively limited number of states to another. In the last chapter, we looked at the series of duration times between the events. In such series, no event was absorbing: it was always possible to pass from any state to another. A different situation arises when an absorbing state exists. The process ends when the individual enters such a state. In the simplest case, only two states exist and the event of interest is the passage from the one to the other. Thus, we are interested in the time during which an individual survives in the first state before passing into the absorbing state, from which there is no return, the survival time.