This is a known issue.  In a comparative Q-Q plot (requested with a CLASS statement) the quantiles of the plotted points and the reference line in each cell are computed using parameters of the distribution fitted to the data in the key cell, which by default is the cell in row 1 and column 1.  When you're using a normal distribution the quantiles are unaffected by this, but that is not the case for distributions with shape parameters.   Currently you do need to use a BY statement to produce independently-fitted Q-Q plots. ... View more

In the RAREEVENTS procedure you can specify alpha values for the lower and upper probability limits independently.  Each defaults to 0.005, for a total probability of 0.01 that a measurement from the (estimated or specified) distribution will fall outside the limits, i.e. the probability of a type I error is 0.01.  That is higher than with a standard 3-sigma limits Shewhart chart, so the default RAREEVENTS limits are more sensitive (narrower).   There is nothing magical about the default alpha=0.005 values.  Using 0.005 instead of 0.00135 (for example) produces a more sensitive chart at the expense of more false positives. ... View more

PROC SHEWHART recognizes four switch variables that you can use to control which subgroups are included in computations and which are displayed on control charts:  http://go.documentation.sas.com/?docsetId=qcug&docsetTarget=qcug_shewhart_sect492.htm&docsetVersion=14.2&locale=en.   This code runs PROC SHEWHART and produces OUTHISTORY= and OUTTABLE= data sets.  Subgroups that are outside the control limits are identified by the _EXLIM_ variable in the OUTTABLE= data set.  The DATA steps set the _COMP_ flag to eliminate those subgroups from the computation, then merge the result with the OUTHISTORY= data set.  The resulting data set is used as a HISTORY= input data set to a second run of PROC SHEWHART, which computes control limits with subgroups outside the original limits eliminated from the computation.   data foo; do group = 1 to 15; do i = 1 to 5; x = rannor(123); if group eq 5 then x + 2; output; end; end; drop i; run; ods html file='switch.htm'; ods graphics / imagemap; proc shewhart data=foo; xchart x * group / markers cout outhistory=foohist outtable=footab odstitle='Control Limits Computed Using All Subgroups'; run; data footab; set footab; if _EXLIM_ ne '' then _COMP_='N'; else _COMP_='Y'; keep group _COMP_; run; data foohist2; merge foohist footab; run; proc shewhart history=foohist2; xchart x * group / markers cout odstitle='Control Limits Computed With Special Causes Omitted'; run; ods html close;   Here are the two charts.  Note that the displayed subgroups are the same but the control limits differ.       I should point out that when you request tests for special causes the OUTTABLE= data set will contain a variable called _TESTS_ that flags the subgroups for which the various tests are positive.  You can write DATA step code to set the _COMP_ flag based on the _TESTS_ value instead of the _EXLIM_ value. ... View more

The ODS style elements that enable you to control the fill colors for the zones independently were added for SAS 9.4.  I don't know of a way to produce a control chart with different colors in the zones in an earlier release. ... View more

Hi Marie-Christine,   PROC SHEWHART does not provide an option to fill the zones with different colors, but you can accomplish this by using ODS Graphics with a modified ODS style.  The following statements produce the chart that is shown below:   data foo;    do group = 1 to 40;       x = rannor(123);       output;    end; run; proc template;    define style Styles.Custom;    parent = Styles.HTMLBlue;       Class GraphColors /          "gzonea" = cxEB6F09          "gzoneb" = cxFFFF68          "gzonec" = cx4A8E5A   ;    end; run; ods listing style=Custom; ods graphics on; proc shewhart data=foo;    irchart x * group /       zonelabels       markers       nochart2       ltmplot=histogram       odstitle="essais irchart"       ; run;     Note that not all the PROC SHEWHART options that apply to traditional graphics output (ODS Graphics disabled), e.g. LZONES=, apply when ODS Graphics is enabled.  ... View more

Hi Howard, It's difficult for me to determine what's going on without seeing the data.  Note that block variables are intended to identify blocks of box-and-whisker charts.  The values of the block variables (abbr and VISIS) should be the same for all observations contributing to one box, i.e. those with the same value of the group variable, n.  Does your data fit that description? Bucky ... View more