Monitoring the Stability of Correlation Structure in Drive Rib Production Process: An MSPC Approach

The stability (or instability) of covariance structure does not ensure the stability (or instability) of correlation structure. However, these stability problems are usually tested using the same approach. The most common and widely used approach is based on likelihood ratio criterion. Unfortunately, its sensitivity is not without limitation, its computational efficiency is low and it is quite cumbersome when the number of variables is large. To overcome these obstacles in monitoring the stability of correlation structure, in this paper we propose a multivariate statistical process control approach by using vector variance as multivariate dispersion measure. First, we investigate the sampling distribution of vector variance of standardized variables and then we construct a control chart. Its sensitivity is very promising, its computational efficiency is high and it is practical even when the number of variables is large. The applicability of the proposed method in monitoring the stability of correlation structure in drive rib production process at Indonesian Aerospace Ltd. will be presented.