Statistical process control
Categories: Business stubs | Statistics | Management | Metrology
Statistical process control (SPC) is a method for achieving quality control in manufacturing processes. It was pioneered by Walter A. Shewhart and taken up by W. Edwards Deming with significant effect by the Americans during the World War II to improve aircraft production. Deming was also instrumental in introducing SPC techniques into Japanese industry after that war.
Any production process will produce objects which vary slightly from their optimal values, even in normal operation. If the production process itself changes (for example, the machines doing the manufacture begin to wear) the distribution of these variables (for example, the overall size or proportions of a widget) will change, until at length the widgets are beyond the tolerances of the consumer and rejected.
There are several forms of SPC; but all of them observe the distribution of the widgets, or some parameter of it, and then test samples of later production to see whether the distribution is changing. In general, this means looking for widgets which are outside the normal range of product, even if they are within tolerance. If the distribution does change, the cause of the change is found and corrected.
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It might be useful to refer to an older version when expanding the article.fr:Maîtrise statistique des procédés