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Date:         Wed, 21 Jan 2004 10:49:44 -0800
Reply-To:     John Fava <jmfava@MSN.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         John Fava <jmfava@MSN.COM>
Organization: http://groups.google.com
Subject:      PROC GLM's "Class" statement (vs. using dummy coding for qual
              variables)
Content-Type: text/plain; charset=ISO-8859-1

Hello,

I'm having difficulty understanding how or when the "Class" statement in PROC GLM (for ANOVA) is used versus simply "dummy-coding" categorical variables for use in the model (also in PROC GLM). Is the "class" statement simply a easier way of dummy coding categorical data, or is there more to this?

Both methods appear to "work," but the output is definitely not comparable. What is the difference?

The data set that I'm working with includes a "test" group, with a "control" group matched up based on several characteristics (four other factors, all categorical, including sex, gender, age and marital status). The dependent variable is continuous. I should also say that this is not a true experimental design ... the control group was created AFTER the experiment was conducted.

If you can answer the "CLASS" issue, I'd also like to understand exactly what's calculated to come up with the LSMEANS.

Thanks!

John Fava


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