Control chart used to monitor shifts in the process mean and variability for multivariate data. This paper aims to monitor process variability through |S| chart. Process variability observed by used the determinant of the sample covariance matrix, which is called |S|. The result of this paper show that the improved |S| chart is more sensitive to shifts in the process variability. The standard |S| chart has a bigger ARL than the improved chart by simulation.

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