Quality and Reliability Methods - SAS

Chapter 19 Reliability and Survival Analysis 365
Univariate Survival Analysis
Table 19.2 Various Weibull parameters in terms of JMP’s alpha and beta (Continued)
Kalbfleisch and Prentice lambda = 1/alpha p = beta
JMP Extreme Value lambda=log(alpha) delta=1/beta
Meeker and Escobar s.e.v. mu=log(alpha) sigma=1/beta
Interval Censoring
With interval censored data, you only know that the events occurred in some time interval. The Turnbull
method is used to obtain non-parametric estimates of the survival function.
In this example from Nelson (1990, p. 147), microprocessor units are tested and inspected at various times
and the failed units are counted. Missing values in one of the columns indicate that you don't know the
lower or upper limit, and therefore the event is left or right censored, respectively. The data may be found in
the sample data files at Microprocessor Data.jmp, and are shown in Figure 19.17.
Figure 19.17 Microprocessor Data
When you launch the Survival platform, specify the lower and upper time limits as two Y columns, count as
Freq and check Plot Failure instead of Survival, as shown in Figure 19.18.
Figure 19.18 Interval Censoring Launch Dialog