Estimating process capability indices for non-normal Pearsonian populations

Clements introduced a method for calculating the estimators of two classical process capability indices (PCI), C_p and C_pk, for non-normal Pearsonian populations. Pearn and Kotz applied Clements' method to obtain first approximation estimators of PCIs for non-normal populations to the two more advanced PCIs, C_pm and C_pmk developed by Chan et al. and Pearn et al. In this paper, we consider a different approach for calculating the estimators of the four PCIs. The new approach may be viewed as a modification of Clements' method. Comparisons between Clements' and the proposed new methods are also provided.