Hi,
I have a within-subject design with four conditions and a covariate
(last column in the design matrix attached). It was created with the
Flexible Factorial in spm5. The model has two main effects (Subject and
Condition), but no "interaction" term for the covariate. I got the
"invalid contrast" message when I tried to set up the following
contrasts to look at the simple effect of a condition or a contrast:
ones(1,12)/12 1 0 0 0 0
zeros(1,12)/12 -1 0 0 1 0
However, I can run the same contrasts with no problem when I took out
the covariate from the model/matrix. Is there a different way to setup
the contrasts when there is a covariate?
Your help is greatly appreciated.
Ben
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