Re: GLM vs unbalanced designs

[John Darrington]

On Sun, Nov 13, 2011 at 10:52:50AM -0500, Jason Stover wrote:
     On Sat, Nov 12, 2011 at 08:22:00AM +0000, John Darrington wrote:
     > I've been reading a bit about two way anova with unbalanced designs.
     > 
     > I concluded that we should have been using what the literature calls 
     > "effects coding" 
http://www.ats.ucla.edu/stat/mult_pkg/faq/general/effect.htm
     > instead of "dummy coding" 
http://www.ats.ucla.edu/stat/mult_pkg/faq/general/dummy.htm which is what we 
have been using until now.
     > 
     > However I tried hacking up a quick change to use "effects coding", but 
     > unfortunately it didn't improve anything.
     > 
     > Am I barking up the wrong tree here?
     
     I just checked Neter, Wasserman and Kutner's "Applied Linear
     Statistical Models", and I think you are right. The model PSPP uses
     has different terms in its model by virtue of dummy coding. The
     discrepancy could be fixed by adding the "effects coding" to
     categoricals.c.
     
I did try that, but got completely way out results.  

Perhaps I made an error somewhere - I'll have another go this week, and 
I'll be a bit more careful about it.

J'

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