David Han, University of Texas at San Antonio
By running the life tests at higher stress levels than normal operating conditions, accelerated life testing (ALT) quickly yields information on the lifetime distribution of a test unit. The lifetime at the design
stress is then estimated through extrapolation using a regression model. In the first part of this talk, a step-stress ALT is considered for progressively Type-I censored exponential failure data with equal step duration. For small to moderate sample sizes, a practical modification is suggested to the censoring scheme in order to guarantee a feasible test, and the optimal step duration is determined under C-optimality, D-optimality, and A-optimality criteria. In the second part of the talk, the optimal constant-stress and step-stress ALTs are compared under complete sampling and Type-I censoring. The efficiency of step-stress ALT relative to constant-stress ALT is discussed in terms of the ratio of optimal objective functions based on the Fisher information matrix.