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Test Design Folio

Test Design Folio Example

This topic presents an example of how to use the test design folio to calculate the number of repairable systems needed to show a specified MTBF at a specified confidence level in a zero-failure demonstration test. An RDT table and plot will also be created in order to examine a variety of different test scenarios.

At the end of a reliability growth testing program for a repairable system, a manufacturer wants to demonstrate that a new product has achieved an MTBF of 10,000 hours with 80% confidence. The available time for the demonstration test is 4,000 hours for each system under test. Assuming zero failures are allowed, determine the required number of systems to be tested in order to demonstrate the desired MTBF.

Follow the steps outlined next to solve for the required number of systems.

According to the folio, if you test 5 systems for 4,000 hours and no failures occur, then you will demonstrate an MTBF of at least 10,000 hours with 80% confidence.

The table appears next. For example, by looking in the second column, you can investigate the test times required in a zero-failure demonstration test, given different numbers of systems being tested.

Like the RDT table, the plot shows the relationship between number of systems and test time, given different numbers of allowable failures. To choose which lines to display in the plot, use the options in the Select Failures area on the control panel. In the following plot, lines for all numbers of allowable failures considered in the table (i.e., 0 to 5) are shown.

 

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