Statistical Process Control

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…problem is resolved, the probability of repeat sales to the customer has been reduced. True SPC demands that the process be characterized and controlled so that defective parts are prevented, not merely detected after they have been produced. Performing statistical process control on a finished part is too late. Gathering enough information about the process to learn what happens, when it happens, and before the problem occurs, is the goal of statistical process control. (Bohn, 1996)