Doug Farel

Chi Squared Distribution for Reliability Demonstration Testing When planning a Reliability Demonstration Test (RDT), your objective is to demonstrate a certain reliability (or MTBF) at a certain Confidence Level (CL). If you want to determine what MTBF at a particular CL you have demonstrated, if you tested T number of hours, you would use the formula listed below. Of course, the actual test time would be dependent upon the Acceleration Factor (AF) and the number of samples on test. The AF will be determined from the acceleration of environment, duty cycle, and/or electrical parameters (voltage, current, or power). A RDT will demonstrate that based upon the test results, the true population MTBF is at least Theta hours at a (1-alpha) CL. The demonstrated MTBF (Theta) for the …

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