Quality and Reliability Methods - SAS

Chapter 19 Reliability and Survival Analysis 355
Univariate Survival Analysis
Figure 19.7 Launch Window for Rats Data
Use the Survival launch dialog to assign columns to the roles as shown in the example dialog above.
Overview of the Univariate Survival Platform
The Survival platform computes product-limit (Kaplan-Meier) survival estimates for one or more groups. It
can be used as a complete analysis or is useful as an exploratory analysis to gain information for more
complex model fitting.
The Kaplan-Meier Survival platform does the following:
• Shows a plot of the estimated survival function for each group and, optionally, for the whole sample.
• Calculates and lists survival function estimates for each group and for the combined sample.
• Shows exponential, Weibull, and lognormal diagnostic failure plots to graphically check the
appropriateness of using these distributions for further regression modeling. Parameter estimates are
available on request.
• Computes the Log Rank and generalized Wilcoxon Chi-square statistics to test homogeneity of the
estimated survival function across groups.
• Analyzes competing causes, prompting for a cause of failure variable, and estimating a Weibull failure
time distribution for censoring patterns corresponding to each cause.
Initially, the Survival platform displays overlay step plots of estimated survival functions for each group as
shown in Figure 19.8. A legend identifies groups by color and line type.
Tables beneath the plot give summary statistics and quantiles for survival times. Estimated survival time for
each observation are computed within groups. Survival times are computed from the combined sample.
When there is more than one group, statistical tests compare the survival curves.