A critical aspect of managing processes is the ability to measure well. Confidence in the integrity of collected data is imperative to ensure that appropriate decisions are made about acceptable product and process changes. It is possible that products declared “out of specification” may be the result of a defective measurement system rather than a poor process.

Costs associated with a poor measurement system can occur from defective product shipped to a customer; unnecessary process changes (i.e., overcontrol); acceptance of poor product; or rejection of good product, leading to unnecessary adjustments. The consequent negative effect on profits is obvious and avoidable. If you’ve ever resampled and retested because initial results were poor, or adjusted a production process based on bad results, only to find that the results got worse, you have likely been “touched” by a poor measurement system. These symptoms are real indicators that measurement is the issue, rather than the process.

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