| Introduced in this talk is a new multivariate exponentially weighted moving average (EWMA) control chart. The proposed control chart, called EWMA V-chart, is designed to detect small changes in the variability of correlated multivariate quality characteristics. It is demonstrated through examples and simulations that the EWMA V-chart is superior to the |S|-chart in detecting small changes in process variability. Furthermore, a counterpart of the EWMA V-chart for monitoring the process mean called the EWMA M-chart is proposed. It is shown that the combination of EWMA M-chart and EWMA V-chart is a better alternative to the combination of MEWMA chart (Lowry, Woodall, Champ and Rigdon(1992)) and |S|-chart. |