What is Failure rate?
'''Failure rate''' is the [[frequency]] with which an engineered [[system]] or [[component]] [[failure|fails]]. Usually it is expressed in a number of failures per time period, like failures per [[hour]]. It is often written as the [[Greek alphabet|Greek letter]] [[λ]] (lambda) and is important in [[reliability theory]]. In practice, the closely related [[Mean Time Between Failures]] is more commonly expressed and used for high quality components or systems. Failure rate usually increases with time. For example, a [[car]] failure rate in its fifth year of service may be many times greater than in the first year of service. Nobody expects to replace an exhaust pipe or worn [[Brake|brake pad]]<nowiki/>s in a new car. Mean Time Between Failures is closely related to failure rate. If the likelihood of failure is constant with respect to time (for example, in some product like a [[brick]] or protected [[steel]] beam), and ignoring the time to recover from failure, failure rate is simply the [[Inverse function|inverse]] of the [[Mean Time Between Failures]] (MTBF). MTBF is an important specification parameter in all aspects of high importance engineering design–such as [[naval architect]]ure, [[aerospace engineer]]ing, [[Mechanical engineer|automotive design]], etc.–in short, any task where failure in a key part or of the whole of a system needs be minimized and stopped, particularly where lives might be lost if such factors are not taken into account. These factors account for many safety and maintenance practices in [[engineering]] and industry practices and government [[Regulation|regulations]], such as how often inspections and overhauls are required on an [[aircraft]]. A similar ratio used in the [[transport industry|transport industries]], especially in [[railway]]s and [[trucking]] is ''''Mean Distance Between Failure'''', a variation which attempts to [[Correlation|correlate]] actual loaded distances to similar reliability needs and practices. Failure rates are important factors in [[insurance]], busines