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This example compares the results for grouped data.
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
|
Termination Time = 100 hours
Result
The book has the following results:
- Beta = 0.753, Lambda = 1.53
- [math]\displaystyle{ \,\!\chi ^{2} }[/math] = 5.5, critical value = 7.8 (Assume significance level = 0.1. Since [math]\displaystyle{ \,\!\chi ^{2} }[/math] < critical value can fail to reject hypothesis that the Crow-AMSAA model fits the data).
Results in RGA
In RGA, 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:
