Australian defence standard for Bayesian reliability demonstration

Abstract

A Bayesian approach to reliability demonstration has been developed by the Australian Department of Defence (Defence) and documented in a handbook. Flexibility was provided to address reliability demonstration requirements relating to probability of success and mean time between failure under both the exponential and Weibull distributions. The handbook was based largely on prior work documented and with the majority of the new work dedicated to ensuring the approach could be practically applied in a contractual environment. The prior work approached the Bayesian reliability demonstration issue through the weighted likelihood form of Bayes' Theorem and incorporated a sequential testing methodology based on the probability of achieving the requirement after each testing phase. An eight step process was developed, consisting of determination of applicability, specification of constraints, determination of weights, construction of the prior, determination of evidence required, testing of the prior, testing and updating and reliability estimation. No pilot project for the handbook had been identified at the time of writing, but the existence of a Bayesian reliability demonstration activity outside of the handbook was noted. It was hoped that this would lead to increased acceptance of Bayesian techniques and postulated that these would eventually become the preferred method of reliability demonstration for Defence.