Example of creating an estimation test planmain topic interpreting results session command see also
Example of creating an estimation test planYou want to run a life test to estimate the 5th percentile for the life of a metal component used in a switch. You can run the test for 100,000 cycles. Before running this life test, you want to determine the number of units to test to ensure a precise estimate.
You expect about 5% of the units to fail by 40,000 cycles, 15% by 100,000 cycles, and the life to follow the Weibull distribution. You want the lower bound of your confidence interval to be within 20,000 cycles of your estimate.
1 Choose Stat > Reliability/Survival > Test Plans > Estimation.
2 Under Parameter to be Estimated, choose Percentile for percent, then enter 5.
3 From Precisions as distances from bound of CI to estimate, choose Lower bound, then enter 20000.
4 From Assumed distribution, choose Weibull.
5 Under Specify planning values for two of the following, do the following:
6 Click Right Cens.
7 Under Type of Censoring, choose Time censor at, then enter 100000. Click OK in each dialog box.
Session window output
Estimation Test Plans
Type I right-censored data (Single Censoring)
Estimated parameter: 5th percentile Calculated planning estimate = 40000 Target Confidence Level = 95% Precision in terms of a one-sided confidence interval that gives a lower bound for the parameter.
Planning Values Percentile values 40000, 100000 for percents 5, 15
Planning distribution: Weibull Scale = 423612, Shape = 1.25859
Actual Censoring Sample Confidence Time Precision Size Level 100000 20000 52 95.0190 |
To estimate the 5th percentile with a one-sided lower confidence bound within 20,000 cycles of the estimate, you must test 52 components for 100,000 cycles.