Grouped Data Reference Example
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This example validates the results for grouped data in Weibull++ Reliability Growth data folios.
Reference Case
MIL-HDBK -189A, Section 6.3.1.7.5, pg. 162, 2009.
For this example, the following will be calculated:
- Parameters of the Crow-AMSAA (NHPP) model
- Demonstrated MTBF (DMTBF)
- Chi-squared goodness of fit
Data
The following table shows the data.
| Failures in Interval | Interval End Time |
|---|---|
| 13 | 20 |
| 16 | 40 |
| 5 | 60 |
| 8 | 80 |
| 7 | 100 |
Result
The book has the following results:
- Beta = 0.753, Lambda = 1.53
- DMTBF = 2.6 hours
= 5.5, critical value = 7.8 (Assume significance level = 0.1. Since
< critical value can fail to reject hypothesis that the Crow-AMSAA model fits the data).
Results in Weibull++
In Weibull++, the Crow-AMSAA (NHPP) model with the maximum likelihood estimation (MLE) method was used to calculate the results.
- The model parameters are:
- The chi-squared goodness-of-fit test results:
- Failure intensity vs. time plot:
