A multivariate EWMA chart consists of:

·    Plotted points, each of which represents the multivariate EWMA statistic for each subgroup.

·    Upper control limit (red), which provides a visual means for assessing whether the process is in control.

Minitab marks points outside of the control limits with a red symbol, which indicates the presence of special causes. When you append the graph to the ReportPad, the complete test results are available. A failed point indicates that a nonrandom pattern exists in the data that may be the result of special-cause variation. You should investigate these points.

You can summarize the multivariate EWMA chart for the dinnerware data as follows:

·    The upper control limit is 8.634. Therefore, you expect the multivariate EWMA statistics to fall below 8.634.

·    None of the subgroup ranges are above the control limit. This chart does not provide any evidence for lack of control. Thus, the process mean vector is in control.