How do I fix the error "A subgroup sample size greater than 25 was encountered" in PROC SHEWHART?


When this message appears:

  ERROR: A subgroup sample size greater than 25 was encountered for process variable <varname>.

then you need to use the XSCHART or SCHART statement instead of the XRCHART or RCHART statement in PROC SHEWHART. If you specify a chart that uses ranges and has subgroup sample sizes greater than 10, the following messages appear in the SAS log:

  WARNING: A subgroup sample size greater than 10 was encountered for process variable <varname>.

  NOTE: For subgroup sample sizes greater than 10, it is statistically more efficient to base control limits on subgroup standard deviations rather than subgroup ranges.