Global Standards for the Microelectronics Industry
failure rate (λ)
The fraction of a population that fails within a specified interval, divided by that interval.
NOTE 1 Standard methods of reporting failure rates of semiconductor devices include 1) percent failed per 1000 hours and 2) FITs.
NOTE 2 The interval may be expressed in operating hours, storage hours, operating cycles, or other units of interval measurement.
NOTE 3 Typically, the term "failure rate" means the instantaneous failure (hazard) rate.
NOTE 4 The statistical upper limit estimate of the failure rate is usually calculated using the χ² (chi-squared) function.