Estimating process capability indices for non‐normal pearsonian populations

Clements 1 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 2 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. 3 and Pearn et al. 4 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.