Hello,
My problem is a very basal one: how to define contrasts. Two
colleagues who followed the SPM course advise differently.
I chose the multi-subject: conditions and covariates design, for
PET scan. The four scans/conditions (A,B,C,D) were entered in
time-order. I want to compare only two conditions (e.g. B and C) in
the analysis. Do I have to put the other conditions on 0 while
defining contrasts (i.e. 0,-1,1,0), or do I have to make another
spm.mat file in which only the two conditions I want to compare are
taken and define contrasts as 1,-1? Is there a difference between the
two ways?
Thanks beforehand,
Marjolein Boshuisen
Drs. Marjolein L. Boshuisen
Arts-onderzoeker
PUK, 6.27
Academisch Ziekenhuis Groningen
Hanzeplein 1/Postbus 30001
9713 GZ/9700 RB Groningen
*31 50 3611523
e-mail: [log in to unmask]
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