In this paper we describe several methods for providing benchmark estimate of the potential width capability of a process when the process becomes stable in the statistical process control (SPC) sense of the word. We define continually meet customer requirements which are expressed in terms of product specifications. Product specifications are generally concerned with both the center and the width of the various characteristics of the process output. The term "capability" is appropriate for process sense. Should the process not be in control, the term "process capability" (Cp) should be replaced by "process performance" (Pp); and the ratio calculations should be based on the capability standard deviation and the performance standard deviation respectively. This point is describes several methods for evaluating the capability standard deviation which do not require the use of control charts. A numerical example is given.
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Holmes, Donald and Mergen, A. Erhan, "Estimating potential capability of an unstable process" (2004). Accessed from
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