Use Generalized Variance
Chart to simultaneously monitor whether the process variability of two or more related variables are in control. This chart is the multivariate counterpart to the R, S, and Moving Range charts.
For example, use a generalized variance chart to monitor temperature and pressure in a plastic injection-molding process. Because temperature and pressure both affect the plastic strength, the engineer wants to monitor these variables at the same time.
Where to find this control chart
To create a generalized variance chart, choose Stat > Control Charts > Multivariate Charts > Generalized Variance.