Concurrent Operating Times - Crow-AMSAA (NHPP) Example

This example appears in the Reliability Growth and Repairable System Analysis Reference book.

Six systems were subjected to a reliability growth test and a total of 81 failures were observed. The following table presents the start and end times, along with the times-to-failure for each system. Do the following:


 * 1)	Estimate the parameters of the Crow-AMSAA model using maximum likelihood estimation.
 * 2)	How many additional failures would be generated if testing continues until 3,000 hours?

Solution


 * 1)	The next figure shows the parameters estimated using RGA.




 * 2)	The number of failures can be estimated using the Quick Calculation Pad, as shown next. The estimated number of failures at 3,000 hours is equal to 83.2451 and 81 failures were observed during testing. Therefore, the number of additional failures generated if testing continues until 3,000 hours is equal to $$83.2451-81=2.2451\approx 3\,\!$$.