A Wald Test for Comparing Multiple Capability Indices

摘要

The capability index CPU is recommended for quality features with a unilateral specification of USL. Linearity, flatness, circularity and cylindricity are examples of such quality features. Here, a Wald statistic is developed for testing the equality of k CPU indices. Industrial data sets are used in illustrations. The procedure is extended for testing the equality of k CPL indices, where the index CPL is used to summarize process performance relative to a single lower specification limit.