The process capability index Cpi , which considers the process variance and departure of the process mean from the target value, is important in the manufacturing industry to measure process potential and performance. This paper extends its applications to calculate the process capability index Cpi_tilda of fuzzy numbers by using Buckley’s approach. In fact, the a-cuts of fuzzy observations are first derived based on various values of a,and then, for each supplier the membership function of fuzzy process capability index Cpi_tilda is constructed based on the a-cuts of fuzzy observations. We apply the Dp,q-distance between fuzzy numbers as a criteria to choose the preferable suppliers. An illustrated example of LED components demonstrates that the proposed method is effective and feasible for the evaluation of competing process capability.

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