Confidence limits for stress-strength reliability involving Weibull models

The problem of interval estimation of the stress-strength reliability involving two independent Weibull distributions is considered. An interval estimation procedure based on the generalized variable (CV) approach is given when the shape parameters are unknown and arbitrary. The coverage probabilities of the CV approach are evaluated by Monte Carlo simulation. Simulation studies show that the proposed generalized variable approach is very satisfactory even for small samples. For the case of equal shape parameter, it is shown that the generalized confidence limits are exact. Some available asymptotic methods for the case of equal shape parameter are described and their coverage probabilities are evaluated using Monte Carlo simulation. Simulation studies indicate that no asymptotic approach based on the likelihood method is satisfactory even for large samples. Applicability of the CV approach for censored samples is also discussed. The results are illustrated using an example. (C) 2010 Elsevier B.V. All rights reserved.