ISO 21747 / DIN 55319 - Process Capability Setup - Grouping Tab

Click the Variables button to display the standard variable selection dialog box, in which you select the variables with the process measurements of interest, and an optional grouping variable with codes to identify to which sample each observation belongs. If a grouping variable is specified, Statistica will compute capability indices (based on the inherent variation) and performance indices (based on the total variation; see ASQC/AIAG, 1991).

Click the Process specs button to display the Enter/edit specification limits dialog box, in which you specify the process (engineering) specification limits from which the capability indices (e.g. Cpk) and performance indices (e.g. Ppk) will be calculated. Note that the Process specs button is only available after Variables have been selected.

The Grouping (process capability/performance) group box contains the options described here:

Select the Constant sample size option button and enter a constant sample size number in the adjacent box (or use the microscrolls) if you do not have a grouping variable but a consistent number of samples for each observation.

Select the Grouping variable option button when you have selected a grouping variable (see Variables above). The variable you selected as your grouping variable is displayed in the adjacent field. The Grouping variable option button is only available if you have specified a grouping variable.

Select the Select all codes check box if you want Statistica to use all of the codes in your grouping variable for your analysis.

Click the Codes button to select the codes that were used in the grouping variable to identify to which sample (group) each observations belongs. Statistica will use only the codes that you specify here for your analysis. This option is only available if a grouping variable was specified (see Variables above).

Select the Keep codes in data file order check box if you want Statistica to keep the codes in the order that they were entered in the data file.

The Estimate sigma from group box is only available if a grouping variable is selected. The Estimate sigma from group box contains three option buttons. Select the appropriate option button to specify if you want to estimate Sigma from either the Ranges, Standard Deviations, or Variances of the values in each group.