This International Standard specifies procedures to test whether an observed value of:
- failure rate;
- failure intensity;
- mean time to failure;
- mean operating time between failures;
complies with a given requirement.
It is assumed (except where otherwise stated) that during the observation period (accumulated relevant test time) the time intervals to or between the failures are independent, and identically exponentially distributed.
NOTE - This assumption implies that the failure rate or failure intensity is constant.
Three types of test plans are prescribed as follows:
- sequential test plans;
- time/failure terminated test plans, including fixed time/failure terminated test plans and alternative time/failure terminated test plans that can be designed to meet a particular need; - fixed calendar time/failure terminated test plans.
General guidance on the choice of test plans is given in 7.3 of IEC 60605-1.