Model Uncertainty in Accelerated Degradation Testing Analysis

In accelerated degradation testing (ADT), test data from higher than normal stress conditions are used to find stochastic models of degradation, e.g., Wiener process, Gamma process, and inverse Gaussian process models. In general, the selection of the degradation model is made with reference to one specific product and no consideration is given to model uncertainty. In this paper, we address this issue and apply the Bayesian model averaging (BMA) method to constant stress ADT. For illustration, stress relaxation ADT data are analyzed. We also make a simulation study to compare the $s\hbox{-}$ credibility intervals for single model and BMA. The results show that degradation model uncertainty has significant effects on the $p\hbox{-}$ quantile lifetime at the use conditions, especially for extreme quantiles. The BMA can well capture this uncertainty and compute compromise $s\hbox{-}$ credibility intervals with the highest coverage probability at each quantile.