We establish reliability goals and measure reliability performance. Goals and measures can be related; however, they’re not the same, and neither do they serve the same purpose.

Recently, I’ve seen a few statements that seem to confuse the role of statistical confidence when establishing a goal. Thus, I’d like to relate how I think about the difference between goals and statistical confidence, along with how they are related.

The purpose of a reliability goal

Setting any goal provides tangible direction or a meaningful target for a team. A reliability goal is a balance of:
• What the customer expects
• What is technically possible
• An expression of business objectives

A reliability goal establishes the probability that a function will successfully operate over a specific duration, given a specific use and environment. For example, my smart phone will make and receive calls in Northern California with a 99-percent probability of successful operation over two years.

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