Hello!
I have the following question that I really need help with!
I have a material consisting of two categorical variables and one
linear variable (age) and I want to examine their influence on the
uptake of a PET tracer in a group consisting only of controls. I'm
using SPM2 for this, and my aim is to find possible interactions
between the factors; both for all three together and two at a time. I
have produced a design matrix using univariate analysis (I've treated
all variables as covariates...), and now my problem is to define the
contrasts. My design matrix has three columns, for the three
"covariates"; is this approach even possible? How do I define the
contrasts?
Hopefully someone can help me with this!
Kristina Wikman
University of Helsinki
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