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MTBF – Mean Time Between Failure

A ‘guesstimate’ of the average, or mean time between design or component failure or disruption in the operation of the product, process, procedure, or design occurs. Mean time between failures assumes that the product can be repaired and the product can then resume it?s normal operations. The repair of such a product is a non-value adding activity.

MTBF is not related with items like expected and/or operating life or other items that in general are not fixed or replacement even though it sometimes may be.

When a failure rate is unvarying, the likelihood that the product will perform without malfunctioning for a time that is equal to or greater than it?s MTBF is only about 37%. This is due to the exponential distribution. A contradiction to the view that there is a 50-50, (or a 50% probability), chance of going beyond the MTBF.

Increases in MTBF may not necessarily result with a proportional rise in reliability. Example …

MTBF of 5 = 82%
MTBF of 10 = .90%
MTBF of 100 = 99%.

MTBF is not the correct tool for all applications, but is a useful measurement of reliability.

Also see MTTF – Mean Time To Failure, Design Life, Durability, Expected Life, Failure Rate, and R ? Reliability.

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Last Updated: Saturday, 10-Jun-06 15:50:57 PDT

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