Subgroup means used to indicate out-of-control points with CONTROLSTAT=MEDIAN in PROC SHEWHART


When the CONTROLSTAT=MEDIAN option is specified on a BOXCHART statement in PROC SHEWHART, the OUTLABEL and COUT options will be applied to subgroup means outside the control limits, whereas they should only be applied to subgroup medians outside the control limits.

There is no direct circumvention for this problem. However, the following approach may provide an alternative when incorrect OUTLABEL results are observed. First specify an OUTTABLE= data set on the BOXCHART statement. Then, in a DATA step, modify the output data set by creating a new label variable for the observations where EXLIM='LOWER' or 'UPPER'. If OUTLABEL=(variable) is specified in PROC SHEWHART, then specify NewLabelVar=(variable) in the DATA step. If OUTLABEL=VALUE is specified in PROC SHEWHART, then specify NewLabelVar=_SUBMED_ . Finally, run PROC SHEWHART again using the option ALLLABEL=NewLabelVar in place of the OUTLABEL= option. The correct subgroups will now be labeled, although the labels will be placed at the means and not the medians.