hi all,
i have a question about conjunctions that i'm sure has been tackled before,
but i can't seem to find the answer.
i have two contrasts across four conditions and all four conditions are
in every session:
task1hit task1miss task2hit task2miss
1 -1 0 0
1 1 -1 -1
in terms of anova, my understanding is
that these two contrasts are mutually
orthogonal in that the rows sum to 0 and the products
of the columns also sum to zero. however when i select
these two contrasts in spm99 on the individual in order
to get the conjunction, it orthogonalizes one with respect
to the other. my question is why is it doing this given that
they are already orthogonal....or are they not?
thanks.
-ian.
***************************
Ian G. Dobbins
MGH-NMR Center
Bldg. 149, 13th Street
Charlestown, MA 02129
(ph) 617-724-9989 (fax) 617-724-7422
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