# Crow Extended Model for Repairable Systems Analysis Example

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

The failures and fixes of two repairable systems in the field are recorded. Both systems started operating from time 0. System 1 ends at time = 504 and system 2 ends at time = 541. All the BD modes are fixed at the end of the test. A fixed effectiveness factor equal to 0.6 is used. Answer the following questions:

- Estimate the parameters of the Crow Extended model.
- Calculate the projected MTBF after the delayed fixes.
- If no fixes were performed for the future failures, what would be the expected number of failures at time 1,000?

**Solution**

- The next figure shows the estimated Crow Extended parameters.
- The next figure shows the projected MTBF at time = 541 (i.e., the age of the oldest system).
- The next figure shows the expected number of failures at time = 1,000.