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 ...

Degradation is a phenomenon where certain measurements of quality characteristics deteriorate over time. When an item subject to life testing is too well made to fail, we often turn our attention to degradation measurements and hope to obtain life time information from this type of data. The first part of this paper presents a general discussion of the degradation phenomenon. The second part re...