Mis-specification analysis of the impact of covariates on the diffusion coefficient in Wiener degradation process

The diffusion coefficients are often assumed irrelevant to stresses in Wiener degradation process. However, there is evidence that the diffusion coefficients under different accelerated stress levels are different in an accelerated degradation test where higher accelerated stress could lead to larger diffusion. Therefore, in contrast to the existing models in which the diffusion coefficients are assumed as a constant or irrelevant to stress …