Hotelling T2, MEWMA, and MCUSUM Results Dialogs - X(Multivariate) Tab; Multiple Stream Results Dialogs - X(XBar) Specs Tab

In the Hotelling T2, MEWMA, and MCUSUM Results dialog boxes, select the X(Multivariate) tab to access the options described here.

In the Multiple Stream X and MR, Multiple Stream X-Bar and R, and Multiple Stream X-Bar and S Results dialog boxes, select the X(XBar) Specs tab to access the options described here.

Element Name Description
General Options Applicable to All Charts
Open specs Click this button to display a standard Open file dialog box, which is used to retrieve previously saved specifications (*.ini files) for the current chart.
Save specs Click this button to display the Select specifications to be saved dialog box. Click OK in this dialog box to display the Save as file dialog box, which is used to save your specifications as an *.ini file.
Set << >> If you have more than one set, these buttons will be available to select which set you want to work with.
Specifications for Hotelling T2, MEWA, and MCUSUM Charts
Center (Estimated/User defined) Click this button (or select the User defined option button) to display a General User Entry Spreadsheet, where you can specify the mean vector that is to be used for the multivariate control chart. Note that these values will only be applied to samples (plot points) that are not explicitly part of another (application) set. See also The Nature of Sets for details.
Sigma (Estimated/User defined) Click this button (or select the User defined option button) to display a General User Entry Spreadsheet for specifying Sigma, to specify the variance/covariance matrix for the multivariate chart. This option enables you to specify a Sigma matrix that was previously computed, e.g., when the process was known to be in-control. See also Computational Details for additional information.
UCL Click this button to display the Upper Control Limit dialog box, which is used to specify the upper control limit for the multivariate chart of means, moving averages, etc. For most multivariate charts, the upper control limit is specified in terms of a probability (p); for other charts (e.g., the MEWMA chart) it is specified in terms of the Average Run Length for the chart.
Warning lines Click this button to display the Warning Lines dialog box, which is used to specify an upper Warning line for the multivariate chart. These are specified using the same "units" as the UCL value (e.g., p, ARL), and are typically set to identify out-of-warning-limits samples with a probability lower than the UCL (and hence, with a greater false-alarm rate).
Specifications for Multi-Stream Charts
Center Click this button to display the Chart center line dialog box, which is used to select the value of the center line of the respective chart instead of the default process mean value.
Sigma Click this button to display the Sigma for dialog box, which is used to specify a particular value of the process sigma. Note that this value will also be readjusted if you change the center line for the variability chart; conversely, if the user changes the value of sigma, then the center line for the variability chart will also be automatically adjusted.

When you click the Sigma button, the respective Sigma for dialog box will be displayed, in which you can specify the variability (sigma) for the respective quality characteristic (for example, for the X-bar chart). This value will be used in the control chart to establish the sigma limits.

Target values for sigma can be derived from experience or from previous similar processes. For a description of the computations involved in standard quality control charts, refer to Computational Details for Multivariate Quality Control Charts.

UCL / LCL Click these buttons to display either the Upper Control Limit dialog box or the Lower Control Limit dialog box, respectively. These dialog boxes are used to change the value of the Upper and Lower Control Limits from their default values of plus/minus 3 times sigma. The UCL (upper control limit) and the LCL (lower control limit) define the lines in the chart that are used to determine whether a particular sample statistic, and thus the entire process, is in control.
Warning lines Click this button to display the Warning lines dialog box, which is used to specify warning lines. Warning limits are often established to alert the quality control engineer if minor deviations from the center line occur in some samples.
If Unequal n This box is used to specify whether to base the chart on the average sample sizes (Use average n), to plot separate control limits for each sample (Use sep. limits), or to plot the standardized (normalized) deviations of the sample means from the target specification (Normalize chart). The average n procedure is satisfactory, as long as the sample sizes do not vary by more than 10%; otherwise, choose one of the two other settings.