A Capability Index Calibrated to the Nonconformance Probability

Process Capability indices have become popular for describing how well a process meets specified tolerances. The lack of affinity with the process nonconformance probability p and the difficulty of dealing with the sampling distribution of their natural estimators affect greatly the use of the traditional indices as Cp , Cpk , Cpm and Cpkm . In this paper, a capability index is proposed which is calibrated to the nonconformance probability. Moreover, Bayesian inference procedures under multinomial sampling are developed for simplifying application of the index in industry.