a b s t r a c tLifetime performance assessment is important in service (or manufacturing) industries. Hence, lifetime performance index C L is used to measure the potential and performance of a process, where L is the lower specification limit. In this paper, assuming the conjugate prior distribution and squared-error loss function, this study constructs a Bayes estimator under the Rayleigh distribution with the progressive type II right censored sample. The Bayes estimator of C L is then utilized to develop a credible interval in the condition of known L. Moreover, we also propose a Bayesian test to assess the lifetime performance of products. Finally, we give two examples and the Monte Carlo simulation to assess the behavior of the lifetime performance index C L . Moreover, the purchasers can then employ the credible interval and the Bayesian test to determine whether the product performance adheres to the required level.