LLN, le 6/11/06
Dear Joel, Cyril and the others,
I had the same (wrong?) feeling as Joel that a contrast like [-1 0 1]
would boil down to [-1 1] and would not take into account condition
B. Seems to me that the recent posts by Jiansong and Jesper tackles
the very same issue. See
<http://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind0611&L=spm&O=D&P=3962>
for the mathematical explanation - which I'm not sure I got correctly...
Now, if Joel is more interested in the C>B>A trend than in the LINEAR
trend, I would suggest using [C-B] masked inclusive by [B-A]. Correct?
Mauro
>Hi,
>How can I look for a linear trend between three (or an odd number of)
>conditions?
>
>EG Conditions A, B, C. Contrast [-1 0 1] finds regions where C>A independent
>of B (I think) but I'd like to find C>B>A.
>
>(I'm not sure that masked contrasts or conjunctions will work but I can't
>quite get my head around that...)
>
>Thanks
>Joel
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Mauro PESENTI
Research Associate, National Fund for Scientific Research (Belgium)
Unite de Neurosciences Cognitives
Departement de Psychologie
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