Defining Variables for . . .  - Quick Tab (n per sample > 1)

The Quick tab of the Defining Variables for . . . dialog box (when n per sample > 1) contains options to select the variables for the analysis, i.e., for which to compute and create quality control charts (for variables). You can either select a Sample identifier variable with codes (sample IDs) to identify the samples in the data, or you can select a Constant sample size (constant n per sample). To specify a multiple-parts Short run chart, select either the Nominal or Standardized short run chart type, and then specify either a Part identifier variable (with part codes/IDs) or a fixed number of samples per part.

Variables

Click the Variables button to display a standard variable selection dialog box. Depending on the selection of the Short run chart and Constant sample size options, either a single variable list, two-variable lists, or three-variable lists selection dialog will be displayed, where you can specify 1) a list of variables for the charts, 2) an optional variable with sample codes (sample IDs; this choice is only provided if the Constant sample size check box is not selected), and 3) an optional variable with part codes (part IDs; this choice is only provided if the Short run chart option is not set to Standard, and the Constant number of samples per part check box is not selected).

Short run chart

Use the options in this box to specify a short run chart for multiple parts. These types of charts are discussed in the Introductory Overviews of the Quality Control Charts module (see Quality Control Introductory Overview - Short Run Charts).

Standard

Select the Standard option button to create a standard non-short run chart.

Nominal

Select the Nominal option button to create a nominal chart where the respective part means are subtracted from the variable values, before the charts are created.

Standardized

Select the Standardized option button to create standardized short run charts, where the sample means or points are standardized within each part (see also, the Glossary term Standardization).

Constant sample size

Select this check box if you do not have a variable with sample identifiers. Specify the sample size for variable control charts by typing the number in the adjacent box or by adjusting the number with the microscrolls.

Constant number of samples per part

If this check box is selected and no part identifier variable is selected, you can specify here a fixed number of consecutive samples for each part. For example, if your input data consist of batches with different specifications (i.e., different parts) from which a fixed number of samples is automatically drawn, then you can select this option so that on reading the data each "chunk" of k consecutive samples is automatically assigned to the same part.

Minimum number of observations per sample

Specify a minimum n per sample by typing it in or by adjusting the number with the microscrolls. Samples with fewer observations than the minimum specified will be ignored.

Lambda

This option is only available for exponentially weighted moving average (EWMA) charts. In this field, specify the value of lambda for constructing the exponentially weighted moving average line (chart). For more information, see Quality Control Computational Details.

Moving average span

This option is only available for moving average (MA) charts. Specify here the span for the n-point moving average line, for the moving average (MA) chart. For more information, see Quality Control Computational Details.