The Words We Use Matter

Abstract

Chris and Fred discuss the different words we often use (and misuse) in reliability engineering. ‘Reliability’ has been used for hundreds of years to describe different concepts of ruggedness, robustness, strength, timeliness, trustworthiness and so on. But – reliability has a specific definition within reliability engineering. There are plenty of other examples of how words we use in reliability engineering can have multiple meanings – even when we think they don’t!

Key Points

Join Chris and Fred as they discuss the different words and terms we use in reliability engineering. And both Chris and Fred have wasted precious hours of their lives watching people debate fruitlessly over what the terms ‘MTBF,’ ‘failure-free period’ and ‘failure mode’ mean? For what? Do these semantics yield a positive outcome?

Topics include:

What is a ‘failure-free period?’ Is it a period that is free of failures? Well … many textbooks say NO! A ‘failure-free period’ is often defined as a period where the probability of failure is sufficiently ‘small.’ What does ‘small’ mean? How ‘small’ is ‘small enough?’ Why do we do this?
Reliability is quality over time. Is it? What is ‘quality?’ Even the most basic literature review on the topics will show that even the pre-eminent standards and ‘gurus’ can’t agree on what quality is? Both Fred and Chris have sat in conversations where for example two engineers argue over whether something a ‘quality failure’ versus a ‘reliability failure.’ Why? In this case, it is mainly about who was responsible for addressing the failure. The customer doesn’t care if a failure is internally classified as a ‘reliability’ versus ‘quality’ failure.
It comes down to intent. If the organization knows what they are ‘intending’ to achieve, it often doesn’t matter what you call the metric. There have been organizations that have very successfully focused the organization on reducing the number of warranty actions customers were initiating. Some of these organizations have classified the fraction of warranty actions as the ‘failure rate.’ This definition is wrong! … if you read a textbook. But who cares (in this case). Every employee of the organization in question knew that ‘failure rate’ was internally describing the fraction of products that suffer warranty failures. And they achieved remarkable results. We often see organizations that have no clear ‘reliability’ intent spawning frivolous conversations about what a ‘fault’ is. Or isn’t.
Use the words that matter. And what matters is based on what you are trying to achieve. If everyone knows what you are trying to achieve, then any discrepancies in word meanings become … trivial!

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