When an OUTHISTOGRAM= data set is specified on the HISTOGRAM statement in PROC CAPABILITY, specification limits that are far away from the data are used and the NOPLOT option is specified, then the OUTHISTOGRAM= data set may contain incorrect values for the variables _MIDPT_ and _OBSPCT_. The data set may contain observed percents at midpoints where no data values actually exist. If instead of the NOPLOT option, a low resolution graph is specified with the LINEPRINTER or LP option, then the histogram bars may also be incorrect. The bars may be drawn where no data points exist.

There is no way to predict with certainty when this problem will occur, but it only happens with spec limits that are many multiples of the data range away from the data. To avoid the problem, either generate a high-resolution histogram along with the OUTHISTOGRAM= data set or omit the spec limits that are too far from the data.