OPTIMUM SIMPLE TIME-STEP STRESS PLANS FOR PARTIALLY ACCELERATED LIFE TESTING WITH CENSORING

H. M. Aly (Saudi Arabia) and A. A. Ismail (Saudi Arabia)

Received November 7, 2007

Abstract

In this paper, time-step stress partially accelerated life tests (PALT) are discussed. The maximum likelihood estimation of the parameters of simple (only two stresses) time-step stress model under type-I censoring is presented. In addition, the confidence intervals of the estimators are constructed. Moreover, optimum time-step stress test plans are obtained. The optimum test plan specifies the optimal stress switching point. Such plans minimize the generalized asymptotic variance of the maximum likelihood estimators for the model parameters. The test units are assumed to follow Weibull lifetime distribution.

Keywords and phrases: reliability, Weibull lifetime distribution, time-step stress test, partially accelerated life test, maximum-likelihood estimation, Fisher information matrix, generalized asymptotic variance, type-I censoring, optimum test plan.