Defining Variables for Hotelling T-Square (Individuals) Chart - Sets Tab

Select the Sets tab of the Defining Variables for Hotelling T-Square (Individuals) Chart dialog box to access the following options.

Option Description
Variable with IDs or Labels to Identify Sets Options on the Specs tab are used to specify a mean vector and variance/covariance matrix (sigma) for the multivariate chart. When sets are specified, the sigma matrix is computed from the respective samples or observations identified as belonging to the same set. Therefore, when sets are specified here, specifications on the Specs tab are ignored.
Set labels Click Set labels to view a standard variable selection dialog box. Select the variable used to determine sets. The variable can contain pre-defined labels. For example, set1, set2, set3 or it can contain a sequence of values that can be used to periodically create new sets.
Note: A new set is also created if specification or control limits change, even if the Set label has not changed.
Create a new set when set label has a value In some 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 Create new set when set label equals to check box and enter 1 in the adjacent box. A new set is started each time the sample number goes back to 1. If this value is set, any other changes in the set identifier are ignored.
Note: A new set is created if specification or control limits change.
Calculate Sigma from first k samples in the set By default, the process sigma 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: The value for k is uniform across all sets. You cannot have a different value for k for different sets.
Chart specs vars for sets Click Chart specs vars for sets to view 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 p-values for this type of chart). Note that set specifications are optional. When these values are defined, sets are automatically created when specs change in consecutive samples.

Click Clear set label/specs to clear the selections made via the Set labels option and the Chart specs vars for sets option that are all selections made in the Defining Sets, Specifications for Charts from Variables dialog box.