Comparison between constant-stress testing and step-stress testing under Type-I censoring Comparison between Constant-stress Testing and Step-stress Testing under Type-I Censoring

By running the life tests at higher stress levels than normal operating conditions, accelerated life testing 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 constant-stress testing, a unit is tested at a fixed stress level until failure or the termination time point of the test, while stepstress testing allows the experimenter to gradually increase the stress levels at some pre-fixed time points during the test. In this work, the optimal k-level constant-stress and step-stress accelerated life tests are compared for the exponential failure data under complete sampling and Type-I censoring. The objective is to quantify the advantage of using the step-stress testing relative to the constantstress one. A log-linear relationship between the mean lifetime parameter and stress level is assumed and the cumulative exposure model holds for the effect of changing stress in step-stress testing. The optimal design point is then determined under C-optimality, D-optimality, and A-optimality criteria. The efficiency of step-stress testing compared to constant-stress testing is discussed in terms of the ∗Corresponding author: [email protected] – The author would like to thank the support from the College of Business research grant program.