I am using a data set in proc shewhart that has 180 observations for each by group combination. I would like to use the 180 observations to calculate all the statistics and display on the chart. However, I would only like to run the tests on the last 30 days. Basically, for the first 120 observations, it should not display if a test was violated or not - only for the last 30 observations.
Is this possible? I don't mind using multiple proc shewhart procedures to get around this issue.
I actually want to chart all 180 observations. I just want it to show test violations in the last 30 observations. There might have been test violations in the first 120 days, but I don't want it to show on the chart.