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Quality and Reliability Methods - SAS

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Chapter 18 <strong>Reliability</strong> Growth 339<br />

Fit Model Options<br />

Figure 18.17 Profilers<br />

Figure 18.18 Factor Settings Window<br />

Reinitialized Weibull NHPP<br />

This option fits an independent growth model to the data from each test phase. Fitting models in this<br />

fashion can be useful when the factors influencing the growth rate, either in terms of testing or engineering,<br />

have changed substantially between phases. In such a situation, you may want to compare the test phases<br />

independently. The Reinitialized Weibull NHPP option is available when a Phase column specifying at least<br />

two phases has been entered in the launch window.<br />

For the algorithm to fit this model, each row that contains the first occurrence of a new phase must contain<br />

the start date.<br />

• Suppose that a single column is entered as Time to Event or Timestamp. Then the start time for a new<br />

phase, with a zero Event Count, must appear in the first row for that phase. See the sample data table<br />

ProductionEquipment.jmp, in the <strong>Reliability</strong> subfolder, for an example.<br />

• If two columns are entered, then an interval whose left endpoint is that start time must appear in the<br />

first row, with the appropriate event count. The sample data table TurbineEngineDesign2.jmp, found in

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