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Re: GLM factorial analysis

From: Jason Stover
Subject: Re: GLM factorial analysis
Date: Fri, 12 Aug 2011 17:37:20 -0400
User-agent: Mutt/1.5.18 (2008-05-17)

On Tue, Jul 26, 2011 at 10:33:56AM +0000, John Darrington wrote:
> See the attached tar file.
> expected.txt is what spss gives (apparently)
> pspp.txt is what pspp gives.
> fdequal.sps is the syntax, which has a test both with and without interaction.
> I hope the problem is clear from this.

I looked into this problem.  Briefly stated, this happens because the
meaning of "type 3 sums of squares" changes in the presence of
interactions.  The fix should be simple enough, but requires get_ssq
to know which variables, if any, went into an interaction. Is there an
easy way to do this?


> J'
> On Mon, Jul 25, 2011 at 02:29:07PM -0400, Jason Stover wrote:
>      On Mon, Jul 25, 2011 at 09:11:21AM +0000, John Darrington wrote:
>      > The sum of squares for factors with interactions are correct, and all 
> the degrees of
>      > freedome are correct.  Unfortunately the ssq for factors without 
> interactions are 
>      > wrong (my experiments showed 3.0 and 3.5 times too high) if the 
> analysis also 
>      > includes interactions between those factors.
>      > 
>      > However, if the analysis is run on the individual variables, without 
> the interactions,
>      > then the results are correct.  
>      > 
>      > So I think the get_ssq function needs some more work.
>      Can you send syntax and output that shows the problems?
> -- 
> PGP Public key ID: 1024D/2DE827B3 
> fingerprint = 8797 A26D 0854 2EAB 0285  A290 8A67 719C 2DE8 27B3
> See or any PGP keyserver for public key.

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