Dear SPM user,
I use a flexible factorial design with three factors in addition to the Subject factor.
The problem is that in SPM8, when adding a covariate to the design, only 3 factors can be chosen in interaction with the covariate.
my question is that if I choose in the design matrix:
main effect and interaction-> interaction-> factors 2 4
and than choose in the covariate: interaction with factor 3
dose the covariate will be in interaction with factor 3 (even not included in the design matrix) or factor 4?
(attached is the batch to clarify my question)
Is there any other way to include interaction of covariate with 4th factor?
Thank you
Yael Weiss
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