Incapability Index with Asymmetric Tolerances
نویسندگان
چکیده
Greenwich and Jahr-Schaffrath (1995) introduced an index Cpp, a simple transformation of the index C∗ pm, which provides an uncontaminated separation between information concerning the process accuracy and process precision. Unfortunately, the index Cpp inconsistently measures process capability in many cases and thus reflects process potential and performance inaccurately. In this paper, we consider a generalization, C′′ pp, to handle processes with asymmetric tolerances. The generalization is shown to be superior to the original index Cpp. In addition, we investigate the statistical properties of a natural estimator of C′′ pp assuming the process is normally distributed.
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