Mean time between failures: Difference between revisions

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'''Mean time between failures (MTBF)''' is the predicted elapsed time between inherent failures of a system during operation.<ref>Jones, James V., ''Integrated Logistics Support Handbook'', page 4.2</ref> MTBF can be calculated as the [[arithmetic mean]] (average) time between [[failure]]s of a system. The MTBF is typically part of a model that assumes the failed system is immediately repaired (zero elapsed time), as a part of a [[renewal process]]. This is in contrast to the mean time to failure (MTTF), which measures average time between [[failure]]s with the modeling assumption that the failed system is not repaired.

The definition of MTBF depends on the definition of what is considered a system [[failure]]. For complex, [[repairable]] systems, failures are considered to be those out of design conditions which place the system out of service and into a state for repair. Failures which occur, that can be left or maintained in an unrepaired condition, and do not place the system out of service, are not considered failures under this definition.<ref>Colombo, A.G., and Sáiz de Bustamante, Amalio: ''Systems reliability assessment &ndash; Proceedings of the Ispra Course held at the Escuela Tecnica Superior de Ingenieros Navales, Madrid, Spain, September 19&ndash;23, 1988 in collaboration with Universidad Politecnica de Madrid'', 1988</ref> In addition, units that are taken down for routine scheduled maintenance or inventory control, are not considered within the definition of failure.

== Overview ==