Approximated optimal designs for a simple step-stress model with type-II censoring, and weibull distribution

This paper deals with theories for approximated optimal design for simple step-stress accelerated life testing (ALT) with type-II censoring, and Weibull distribution. Statistically approximated optimal ALT plans are developed to minimize the asymptotic variance of the maximum likelihood estimators (MLE) of the p-th percentile of lifetime at design stress. For the complex of calculating the expectation of order statistics, the Fisher information matrix for type-II censored data is approximated by that for type-I censored data. The approximated optimal plan doesn´t depend on the values of accelerating model parameters. Simulation results also show that the optimal stress levels are highest possible stress and lowest possible stress.