Measuring process capability index C″p(u, v) for fuzzy data and fuzzy requirements
by Daniel Grau
International Journal of Quality Engineering and Technology (IJQET), Vol. 3, No. 4, 2013

Abstract: Process capability indices are quantitative measures on process performance. The C″p(u, v) indices family depending on two parameters allows to generalise the common indices used in industry. Ordinarily the process data and process requirements are assumed to be precise numbers. In practical situations, however, it is more realistic to assume that they are more or less imprecise. Such observations are called fuzzy. This paper presents a family of fuzzy indices for processes where the observations, the specification limits and the target are fuzzy. The membership function of fuzzy capability indices is constructed on the basis of the α-cuts of fuzzy data. A three-decision testing rule is developed to assess process performance based on p-values or critical values. With precise values the suggested approach boils down to the usual binary decision. A real example with a linguistic variable illustrates the setting up of the said method.

Online publication date: Sat, 19-Jul-2014

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