Defining Variables for Multivariate CUSUM Chart - Sets Tab

Select the Sets tab of the Defining Variables for Multivariate CUSUM Chart dialog box to access the options described here.

Variable with ID's or Labels to Identify Sets. Note that the options on the Specs tab enable you to specify a mean vector and variance/covariance matrix (sigma) for the overall multivariate chart. When sets are specified here, the sigma matrix will be computed from the respective samples or observations identified as belonging to the respective same set. Therefore, when sets are specified here, specifications on the Specs tab of this dialog will be ignored.

Set labels

Click the Set labels button to display a standard variable selection dialog box, where you can select the variable that will be used in determining sets. This variable can contain pre-defined labels (i.e., set1, set2, etc.) or it can contain a sequence of values that Statistica can use to periodically create new sets (see the Create new set when set label equals to option description below). Note that a new set will also be created if specification or control limits change, even if the Set label has not changed.

Create new set when set label equals to

In certain applications, sets are identified by a cycling sequence number rather than a label. For example, samples are taken every ten minutes and within any given hour, the sample is labeled as 1, 2, 3, 4, 5, or 6. To create sets based on the samples taken in one hour, select the Create new set when set label equals to check box and enter 1 in the adjacent box. Each time the sample number goes back to 1, a new set will be started. If this value is set, any other changes in the set identifier are ignored; only when the set identifier transitions back to the specific value (e.g., 1) will a new set start. Note that a new set will also be created if specification or control limits change.

Calculate Sigma from first k samples in the set; k =

By default, the process sigma (matrix) is calculated on a per set basis using every sample in the set. If you want to calculate sigma using only the first k samples in each set, select the Calculate Sigma from first k samples in the set check box and enter a value for k in the adjacent k= box. Note that the value for k is uniform across all sets, i.e., you cannot have a different value for k for different sets.

Chart specs vars for sets

Click this button to display the Defining Sets, Specifications for Charts from Variables dialog box. Use the options in this dialog box to define the variable specifications (multivariate Center line, or mean vector), control limits, and warning limits (defined as average run length values for this type of chart). Note that set specifications are optional. When these values are defined, sets will automatically be created when specs change in consecutive samples.

Clear set label/specs

Click this button to clear the selections made via the Set labels option and the Chart specs vars for sets option (i.e., all selections made in the Defining Sets, Specifications for Charts from Variables dialog).