Estimation of constant-stress accelerated life test for Weibull distribution with nonconstant shape parameter

Statistical inference is considered on constant-stress accelerated life test when the failure data are progressively Type-II censored. Under the assumption that the Weibull shape parameter is nonconstant and both Weibull parameters follow log-linear life-stress model with stress, the unknown coefficient parameters are estimated by using methods of maximum likelihood and expectation-maximization based estimations as well as approximation maximum likelihood estimation. The confidence intervals of unknown parameters are also constructed based on asymptotic theory and bootstrap technique. Simulation study and a real data example are presented for illustrative purpose.