Optimum Simple Ramp-Tests for the Weibull Distribution and Type I Censoring

Abstract

This paper presents an optimum simple ramp test - accelerated life test with two different linearly increasing stresses - for the Weibull distribution under type I censoring. It is assumed that: 1) the inverse power law holds between the Weibull scale parameter and the constant stress, and 2) the cumulative exposure model for the effect of changing stress applies. The optimum plan - low stress rate and proportion of test units allocated to low stress mode - is found which minimizes the asymptotic variance of the maximum likelihood estimator of a stated quantile at design stress. For selected values of the design parameters, these optimum plans are tabulated, and the effect of the pre-estimates of these parameters are studied.