Hi Kimberley, Could you post a code snippet of what you're trying to do? There are many different charts which can be produced by proc shewhart, and they have different default behavior for control limits based upon the underlying statistical assumptions. I see the "xsxhart" tag- is that really the "xschart" statement? In the SAS/QC user's guide, there are a couple examples in the "xschart" section showing control charts with fixed limits.
title 'Mean and Standard Deviation Charts for Power Output';
proc shewhart data=Turbine;
xschart KWatts*Day ;
run;
If you wish to set your own limits, such as when you have limits created on an initial set of data, and wish to apply them to a new set of data, the the answer is to use the "LIMITS=" option to the PROC SHEWHART statement http://support.sas.com/documentation/cdl/en/qcug/63964/HTML/default/viewer.htm#qcug_shewhart_a0000003570.htm This option will read in a dataset produced by a previous run of the procedure. Here is an example for a p-chart: http://support.sas.com/documentation/cdl/en/qcug/63964/HTML/default/viewer.htm#qcug_shewhart_a0000003737.htm First, generate the dataset with the limits you want using the OUTLIMITS dataset. This example uses the pchart statement, but it should be almost identical for the xschart statement if that's what you're using.
title 'Proportion of Circuit Failures';
proc shewhart data=CircOne;
pchart Fail*Batch / subgroupn = 500
outindex = 'Trial Limits'
outlimits = Faillim1
odstitle = title;
run;
Then read that data set, "Faillim1", in when running PROC SHEWHART the next time. (see the documentation for a more complicated version)
title 'p Chart with Revised Limits for Failed Circuits';
proc shewhart data=CircOne limits=Faillims1;
pchart Fail*Batch / subgroupn = 500
readindex = 'Revised Limits'
vref = 0.0156 0.032226
vreflabels = ('Trial P' 'Trial UCL')
vreflabpos = 3
odstitle = title
nolegend;
label Fail = 'Fraction Failed'
Batch = 'Batch Index';
run;
ods graphics off;
Let me know if this helps, but it sounds like you might have figured it out. Please post any code if you have any specific issues you'd like help with.
... View more