ratio between the time durations necessary to obtain the same stated number of failures or degradations in two equal size samples, under two different sets of stress conditions involving the same failure mechanisms and fault modes and their relative prevalence, kahe samase proovi puhul sama arvu rikete või hälvingute saamiseks vajalike ajavahemike suhe kahes erinevas pingetingimuses, mis hõlmavad samu rikkemehanisme ja rikkeliike