MTBF use and thinking is still rampant. It affects how our peers and colleagues approach solving problems, and there is a full range of problems that come from using the “mean time between failure” (MTBF) metric.

So, how do you spot the signs of MTBF thinking even when MTBF is not mentioned? Let’s explore some approaches that you can use to ferret out MTBF thinking and move your organization toward making informed decisions concerning reliability.

Ask, ‘What do you really want?’

Really, it is just that simple. Ask what it is you really mean about durability or how long the item should work or something similar. If someone asks for MTBF, they often are interested in the probability of failure over some duration within some set of conditions.

Asking for MTBF provides an inverse of the average failure rate—not at all what they may really have wanted to know.

If they really want the average inverse failure rate, ask them why? What decision are they going to make using that information? Is knowing MTBF the right information to inform the pending decision? If not—and MTBF, as you know, is not generally informative at all—suggest using reliability (i.e., probability of failure over a time period).

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