In this example, 50 capacitor units are tested at three temperatures (85o, 105o, and 125o Celsius) for 1500 hours. The results are recorded in the Capacitor ALT.jmp sample data table. The resulting model is used to predict the fraction of the population that is failing at 100,000 hours at normal use temperature of 25o Celsius.
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2.

Click the green triangle to run the Fit Life by X table script.

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Click 105 above Temp and change it to 25.

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Click 750.5 above Hours and change it to 100,000.

Based on your current study, the predicted fraction of the population that fails at 25o at 100,000 hours is 0.00358, with a confidence interval of 0.00056 to 0.02268. You want to estimate the failure fraction more precisely. To decrease the width of the confidence interval, augment your study with additional tests.
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Enter 5 for Number of Levels.

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6.

Click Continue.

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Enter 85, 90, 105, 110, and 125 for the Temp Level Values.

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9.

Under Prior Mean, enter the acceleration model parameter estimates from the Fit Life by X Estimates report, found in the Weibull Results report on the Statistics tab.

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Enter 35.200 for Intercept.

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Enter 1.389 for Temp.

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Enter 1.305 for scale.

For the Weibull distribution, JMP uses a parameterization that depends on a location parameter μ and scale parameter σ. In terms of the usual α and β parameterization, the scale parameter is σ = 1/β. See JMP’s Weibull Parameterization.
10.

Under Diagnostic Choices, enter 100,000 for both boxes for Time range of interest. Leave the Probability of interest value set to 0.1.

11.

Under Design Choices, enter 1500 for Length of test.

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Enter 250 for Number of units under test.

Completed Design Details Window shows the completed Accelerated Life Test Plan outline.
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Click Continue.

14.

To account for the units at each setting of Temp in the previous experiment, enter the following under Candidate Runs.

15.

From the ALT Plan red triangle menu, select ALT Optimality Criterion > Make Probability IOptimal Design.

This tells JMP to use the Probability optimality criterion when creating the design in step 16. For details about this criterion, see Make Probability IOptimal Design.
16.

Click Make Design.

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50 units at 85o. Since the previous experiment already tested 50 units at 85o, no additional units are needed.

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50 units at 105o. Since the previous experiment test 50 units at 105o, no additional units are needed.

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0 units at 110o. The next experiment will not test any units at this level.

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61 units at 125o. Since the previous experiment test 50 units at 125o, 11 additional units are needed.
