Optimum quadratic three-step stress plans for log-logistic distribution

摘要

This paper presents three-step stress test plans, which assume that a quadratic relationship exists between the mean of log life time and the stress. A log-logistic distribution and a cumulative exposure model are assumed. Tables of optimum times of changing stress level are obtained by minimizing, with respect to the change times, the asymptotic variance of the maximum likelihood estimator of a given 100 P-th percentile of the distribution at the design stress.