I have a normal process (Anderson-Darling pvalue=.54 and skew=.3. The median
The R chart is out of control (1 outlier). This means that theprocess variability is unstable, and the control limits on the xbarchart are unreliable. The process is not stable over time. What ifanything does this have to do with choosing the center of thedistribution? Use the median in this instance. Outliers will notaffect median as much as the mean. That is my best guess.
