Overtesting should be done when (a) testing by variables is impractical because of time and cost considerations or because the probability distribution of stress to failure cannot be estimated with sufficient accuracy, and (b) an unrealistically large number of parts would have to be tested at the specification stress for the necessary confidence and survival probability.

1.1 This guide covers the use of overtesting in order to reduce the required number of parts that must be tested to meet a given quality acceptance standard. Overtesting is testing a sample number of parts at a stress level higher than their specification stress in order to reduce the amount of necessary data taking. This guide discusses when and how overtesting may be applied to forming probabilistic estimates for the survival of electronic piece parts subjected to radiation stress. Some knowledge of the probability distribution governing the stress-to-failure of the parts is necessary, although exact knowledge may be replaced by over-conservative estimates of this distribution.