New format available! This reference is now available in a new format that offers faster page load, improved display for calculations and images and more targeted search.
As of January 2024, this Reliawiki page will not continue to be updated. Please update all links and bookmarks to the latest references at RGA examples and RGA reference examples.
This example validates the results for grouped data in RGA.
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:
