This tutorial provides a brief conceptual background to the practice of SPC, as well as the necessary formulas and techniques to apply it. Shewhart devised control charts used to plot data over time and identify both Common Cause variation and Special Cause variation. Deming relabeled chance variation as Common Cause variation, and assignable variation as Special Cause variation.īased on experience with many types of process data, and supported by the laws of statistics and probability, Dr. Shewhart identified two sources of process variation: Chance variation that is inherent in process, and stable over time, and Assignable, or Uncontrolled variation, which is unstable over time - the result of specific events outside the system.
After early successful adoption by Japanese firms, Statistical Process Control has now been incorporated by organizations around the world as a primary tool to improve product quality by reducing process variation.ĭr. Edwards Deming, who introduced SPC to Japanese industry after WWII. Walter Shewhart of Bell Laboratories in the 1920's, and were expanded upon by Dr. The concepts of Statistical Process Control (SPC) were initially developed by Dr. MoreSteam Hint: As a pre-requisite to improve your understanding of the following content, we recommend that you review the Histogram module and its discussion of frequency distributions.
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