Wiktionary
n. The frequency with which an engineered system or component fails, expressed for example in failures per hour.
Wikipedia
Failure rate is the frequency with which an engineered system or component fails, expressed in failures per unit of time. It is often denoted by the Greek letter λ (lambda) and is highly used in reliability engineering.
The failure rate of a system usually depends on time, with the rate varying over the life cycle of the system. For example, an automobile's failure rate in its fifth year of service may be many times greater than its failure rate during its first year of service. One does not expect to replace an exhaust pipe, overhaul the brakes, or have major transmission problems in a new vehicle.
In practice, the mean time between failures (MTBF, 1/λ) is often reported instead of the failure rate. This is valid and useful if the failure rate may be assumed constant – often used for complex units / systems, electronics – and is a general agreement in some reliability standards (Military and Aerospace). It does in this case only relate to the flat region of the bathtub curve, also called the "useful life period". Because of this, it is incorrect to extrapolate MTBF to give an estimate of the service life time of a component, which will typically be much less than suggested by the MTBF due to the much higher failure rates in the "end-of-life wearout" part of the "bathtub curve".
The reason for the preferred use for MTBF numbers is that the use of large positive numbers (such as 2000 hours) is more intuitive and easier to remember than very small numbers (such as 0.0005 per hour).
The MTBF is an important system parameter in systems where failure rate needs to be managed, in particular for safety systems. The MTBF appears frequently in the engineering design requirements, and governs frequency of required system maintenance and inspections. In special processes called renewal processes, where the time to recover from failure can be neglected and the likelihood of failure remains constant with respect to time, the failure rate is simply the multiplicative inverse of the MTBF (1/λ).
A similar ratio used in the transport industries, especially in railways and trucking is "mean distance between failures", a variation which attempts to correlate actual loaded distances to similar reliability needs and practices.
Failure rates are important factors in the insurance, finance, commerce and regulatory industries and fundamental to the design of safe systems in a wide variety of applications.
Usage examples of "failure rate".
Had it been interested in such things, it might have reflected that such a low failure rate was near miraculous, but this computer lacked even the most rudimentary of awarenesses.
Qeng Ho coldsleep boxes were so safe that the failure rate was a kind of statistical guess, at least under proper use and for spans of less than 4Gsec.
R&D promised the failure rate would drop, but the most optimistic success rate projected, even for the fully matured technology, was no more than forty to fifty percent.
Today Invincible's weapons would be live-fired for the first time, and given the extraordinary failure rate of much of their equipment, the tension in the mess was thick enough to chew.
That's only a twenty percent failure rate, and I don't think Mara was really a failure.
The Indian failure rate was a whopping forty per cent, and the toll in lost lives, on those crowded space trucks, was immense.
Their failure rate has never fallen below sixty-five percent, but they’.
You wait and see: if the Soviets ever open the books and let us compare duds and destructs, you'll find out they had a failure rate much higher than ours.
This is probably the extreme failure rate, but it does point out a major problem with clamps.
We're facing a ten percent failure rate-many of them leading to death.
For some reason, the bodies into which I have been placed suffer an abnormally high failure rate.
But I found out that Conselline Sept has major investments in development companies, and their projections for the rate at which excess population can be absorbed by development make no senseunless theres a much higher failure rate than before.