Quality and Reliability Methods - SAS

Chapter 2 Statistical Control Charts 29
The Control Chart Launch Dialog
Sample Label
The Sample Label role enables you to specify a variable whose values label the horizontal axis and can also
identify unequal subgroup sizes. If no sample label variable is specified, the samples are identified by their
subgroup sample number.
• If the sample subgroups are the same size, check the Sample Size Constant radio button and enter the
size into the text box. If you entered a Sample Label variable, its values are used to label the horizontal
axis. The sample size is used in the calculation of the limits regardless of whether the samples have
missing values.
• If the sample subgroups have an unequal number of rows or have missing values and you have a column
identifying each sample, check the Sample Grouped by Sample Label radio button and enter the
sample identifying column as the sample label.
For attribute charts (P-, NP-, C-, and U-charts), this variable is the subgroup sample size. In Variables
charts, it identifies the sample. When the chart type is IR, a Range Span text box appears. The range span
specifies the number of consecutive measurements from which the moving ranges are computed.
Note: The rows of the table must be sorted in the order you want them to appear in the control chart. Even
if there is a Sample Label variable specified, you still must sort the data accordingly.
The illustration in Figure 2.4 shows an X -chart for a process with unequal subgroup sample sizes, using the
Coating.jmp sample data from the Quality Control sample data folder.