This option in the Define Characteristic dialog box Property tab is only available for Attribute (P, U, Np, C) control charts. The sample size is used to determine the control limits for these charts.
Select either:
Constant: (Required for Np and C Charts) Enter the sample size used during data collection. This is the number of items inspected, only some of which will meet the criteria of interest (for example, be defective). In this case, each data period (plotted point) must use the same sample size.
Variable: (Available only for P and U Charts) Select this option if each data period may use a different sample size. The Data Form or Spreadsheet will provide a field for entering the sample size for each data period.
Default Count: Enter a value that will be automatically entered as the default number of defects (or defectives) within each sample group.
See also: