Some Problems in the Study of Non-Normal Process Capability Indices

It is one of the current hotspots in the analysis of process capability to study the process capability indices(PCIs) for non-normal distributions.Aiming at some problems existing in this domain,this paper analyzes the importance of normality assumption,points out the causations and consequences related to non-normal distributed processes,and presents the way to carry out the normality test for univariate and multivariate distributions of quality attributes.Then the paper categorized and discusses briefly usual methods for the estimation of non-normal capability indices.Included in the paper are some issues in the study of non-norml capability indices that need more attentions.