An exponential reliability-growth model in multicopy testing program

An exponential reliability-growth model, which incorporates step changes in the failure intensity, is proposed as an alternative to other reliability-growth models commonly used to analyze the failure process of repairable equipment in a development program. A multicopy testing-modification scenario is used in which several s-identical copies are put on test, and design modifications are introduced into all copies at each failure occurrence. Maximum likelihood estimation of quantities which index the reliability of the equipment as it goes into production, is investigated under the hypothesis that the unconstrained estimators are inside the parameter space. Exact and approximate procedures for obtaining interval estimates of the current failure intensity and interval prediction of the current lifetime are provided. A goodness-of-fit test is developed, and exact critical values of the test statistic are given. The situations in which unconstrained results can be correctly used are investigated and a numerical application drawn from real data is presented.