This tool provides the ability to plan a sequential reliability demonstration test for verification of equipment mean time between failure (MTBF), assuming an exponential failure distribution. Input parameters include the following:
Lower test MTBF(θ1). The test plan will reject an item whose true MTBF is θ1 with a probability of 1 - β.
Upper test MTBF(θ0). The test plan will accept an item whose true MTBF is θ0 with a probability of 1 - α.
θ0 = d * θ1.
Discrimination ratio (d). The discrimination ratio is one of the standard test plan parameters which establishes the test plan envelope. d = θ0/θ1.
Consumer’s risk (β). The consumer’s risk is the probability of accepting an equipment
with a true MTBF equal to the lower test MTBF (θ1).
Producer’s risk (α). The producer’s risk is the probability of rejecting an equipment
with a true MTBF equal to the upper test MTBF (θ0).
True MTBF. The MTBF that would be observed if an infinite number of units were tested for an infinite amount of time.
See reference 1, chapter 24, for a more detailed discussion on sequential reliability testing and this blog post for an example. The Operating Characteristic (OC) curve is generated using Equation 7 in Reference 6.