Fuzzy process capability plots for families of one-sided specification limits

Process capability indices (PCIs) have been popularly used in the manufacturing industry for measuring process potential and performance. When our data are imprecise, classical PCIs are improper. In this paper, a graphical approach has been presented for monitoring whether or not our process is capable by using the process capability plots for two families of the one-sided PCIs based on fuzzy data. The presented methodology takes into consideration the certain degree of imprecision on the sample data and leads to the three-decision rule that has been presented on the process capability plot. Also, the advantages of this method in comparison to the fuzzy hypothesis test have been discussed. Two real examples have been presented to demonstrate this approach.