Another way to discriminate between different probability distributions is to use graphical diagnostics. In Chapter 3 we saw how to use plots of the estimated survivor function to evaluate two of the distributional models considered in this chapter. Specifically, if the distribution of event times is exponential, a plot of – log Ŝ(t) versus t should yield a straight line with an origin at 0. If event times have a Weibull distribution, a plot of log[–log Ŝ(t)] versus log t should also be a straight line. These plots can be requested in PROC LIFETEST with the PLOTS=(LS, LLS) option in the PROC LIFETEST statement.

Output 4.9 shows the log-survivor plot for the recidivism data. The graph is approximately ...

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