If both charts are now in control, extend the control limits for ongoing monitoring. An important consideration in using X-bar/R charts is the selection of an appropriate subgroup or sample size.

When you are working with subgrouped data, it can be helpful to accompany a cusum chart for means with a Shewhart s chart for monitoring the variability of the process. This example creates this ...

For example, the -chart control limits for the choral room in ... = 0.65, b4 = 1.34. Figures 1 and 2 represent the s-chart and the -chart; both in-control. The next step computes the process ...

Example 38.4: Creating a Chart with Revised Control Limits See SHWPEX4 in the SAS/QC Sample Library The following statements create a SAS data set named CIRC_ONE, which contains the number of failing ...