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Track 1 Session 3
1:00 to 2:00 p.m. Wednesday,
October 22, 2008
Trapped by MTBF: A Study of Alternate Reliability Metrics
MTBF is probably the most common metric used to describe the reliability of a product, but it is perhaps the least understood and most
misleading metric as well. What do we really mean by MTBF and how much information does it really give us? We find that it is very difficult to
write reliability plans with only MTBF as the metric. It is difficult to allocate down to subassemblies, and it is difficult to measure where we are
against our goals.
When we use MTBF, we make generalized assumptions such as constant failure rate, and these assumptions are not only rarely true, but also
cause us to miss meaningful information relative to the design attributes of our product, especially in what happens in the early life portion and
in the wear-out portion of our product life. For us to perform a robust Design for Reliability (DFR) process, we must include all areas of our
product life, not just the steady state portion. In this presentation, we shall discuss a number of other more descriptive and useful metrics
(including Reliability, DOA, AFR, Life and others) to help describe product reliability in a richer context.
Key Words: Reliability, MTBF, MTTF, Non-repairable, AFR, DOA, Exponential, Weibull
Mike Silverman
Ops A La Carte |
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