Reliability tests are commonly used in product design and manufacturing processes to assure the reliability of components, subsystems, and, in some cases, complete systems. Typical responses are time to failure (either in terms of operating time or number of cycle of operation) or strength or other critical material properties. Virtually all
laboratory reliability tests are accelerated (e.g., by testing at an increases cycling rate or at higher-than-usual levels of temperature or voltage) so that information is obtained in a timely manner. The resulting test data are often censored because not all units fail by the end of the test.