Quality and Reliability Methods - SAS

336 Reliability Growth Chapter 18
Fit Model Options
Figure 18.14 Fixed Parameter Crow AMSAA Report
Piecewise Weibull NHPP
The Piecewise Weibull NHPP model can be fit when a Phase column specifying at least two values has been
entered in the launch window. Crow-AMSAA models are fit to each of the phases under the constraint that
the cumulative number of events at the start of a phase matches that number at the end of the preceding
phase. For proper display of phase transition times, the first row for every Phase other than the first must
give that phase’s start time. See “Multiple Test Phases” on page 325. For further details about the algorithm,
see “Statistical Details for the Piecewise Weibull NHPP Change Point Detection Report” on page 348.
When the report is run, the Cumulative Events plot updates to show the piecewise model. Blue vertical
dashed lines show the transition times for each of the phases. The Model List also updates. See Figure 18.15,
where both a Crow-AMSAA model and a piecewise Weibull NHPP model have been fit to the data in
TurbineEngineDesign1.jmp. Note that both models are compared in the Model List report.