MIL-STD-781C fixed time test: effect of redundancy

When a fixed-time test is used to demonstrate the mean time between failures (MTBF) of a system containing redundancy, the alpha and beta risks vary as a function of MTBF and also as a function of the percentage of redundancy within the system and the number of systems being tested. An algorithm is presented for calculating the probability of zero to five system failures during a fixed-time reliability demonstration test for a system containing redundancy. The probability equations are developed as a function of MTBF, test time, and the percentage of redundancy within the system. Of particular note is the increased beta risk occurring when the MTBF demonstration consists of two or more systems containing redundancy.<
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