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We consider a k -step step-stress model under Type-I censoring. We obtain the maximum likelihood estimates (MLE) of the parameters assuming a cumulative exposure model with lifetimes being lognormal distributed. A two-stage algorithm integrating a modified simulated annealing algorithm with a Newton-Raphson method is proposed to compute the MLE of the parameters. We also derive the confidence intervals for the parameters using asymptotic distributions, a likelihood ratio test, and parametric bootstrap resampling methods. The performance of the point and interval estimation of the parameters are evaluated through a Monte Carlo simulation study.
Date of Publication: June 2012