The bathtub curve traces the hazard rate, the instantaneous failure rate among units still working, across a population's life. The early infant mortality region falls as weak units drop out, the long flat floor is the useful life with a roughly constant random failure rate, and the wear-out wall rises as fatigue, corrosion or electromigration take over. Many real products show only one or two of the three regions.
Field returns look like the left wall of the bathtub curve: lots of fails in the first month, then almost none.
Also heard as
- bathtub
- life curve
Related terms
Infant mortality
Early-life failures caused by manufacturing flaws, giving a failure rate that starts high and then falls.
Burn-in
Operating products under raised stress before shipment so weak units fail in the factory instead of in the field.
Weibull distribution
Flexible life distribution with a shape and a scale parameter, the standard model for fitting time-to-failure data.
Shape parameter
Weibull beta: the slope of a Weibull plot, which shows whether failures are early-life, random or wear-out.
MTBF
Mean time between failures: average operating time between successive failures of a repairable system.