QualiPedia: Statistical Process Control (SPC)

Statistical process control might be the most misunderstood approach to quality improvement

Published: Wednesday, July 22, 2009 - 14:52

Search the internet for “What is SPC?” and there are many definitions and descriptions of statistical process control that are correct but not complete. They are true but not the whole truth.

From the search results, a general definition and description of SPC could be as follows.

Definition: SPC is the application of statistical tools and techniques to find, analyze, and control variation in processes.

Description: Find. Monitor, measure, and collect data using tools such as control charts for variables data(i.e., average/range charts, average/standard deviation charts, run tests, etc.) and control charts for attributes data (i.e., c charts, p charts, u charts, etc.) Analyze. Through descriptive analysis of data and charts (using histograms, Pareto charts, scatter plots, etc.) Control. Employ techniques for problem solving (brainstorming, critical thinking, using fishbone diagram, flowcharts, etc.) and for process capability (capability ratio—Cr, performance ratio—Pr, capability index—Cp, process capability—CpK, etc.)

With so many ways of obtaining data and attaining knowledge, how could this description not be complete answer to “What is SPC?”

The description falls short in explaining what to do with the attained knowledge. How do you apply and develop the knowledge beyond its usefulness in monitoring processes for corrective actions or maintaining status quo.

“Control charts are effective only to the extent that the organization can use the knowledge. Knowledge gathering is in vain without an organization that can disseminate and use this knowledge,” says statistician Donald J. Wheeler. “While it is easy to focus on the tools, and while it is easy to teach the tools, the tools are secondary to the way of thinking. Learn the tools and you will have nothing. You will not know what to do. You will not know how to use the tools effectively. Learn and practice the way of thinking that undergirds the tools and you will begin an unending journey of continual improvement.”

Sources:

http://www.spcpress.com/pdf/DJW129.pdf

http://www.theqcgroup.com/calendar/detail.php?id=23

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About The Author

Laurel Thoennes @ Quality Digest

Laurel Thoennes is an editor at Quality Digest. She has worked in the media industry for 33 years at newspapers, magazines, and UC Davis—the past 25 years with Quality Digest.

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