Multivariate Process Capability Index: A Review and Some Results

Process capability is defined as inherent variability of a process which is running under chance cause of variation only. Process capability index is measuring the ability of a process to meet the product specification limit. Generally Cp and Cpk have been widely used as statistical tools to assess the manufacturing process performance. These indices provide numerical measures on process precision, process accuracy and process performance. The multivariate process capability indices, which are used for evaluation of processes with correlated quality characteristics are considered as new emerging research area. In this paper, we describe an approach of estimating multivariate process capability indices assuming multivariate g-and-h distribution and illustrate their performance using simulated and practical data set.