hi volkmar.
dear volkmar (and others).
Thanks for your help with the explanation about my problem in which i would
like to test the difference between two groups according the correlation of
painexperience with the BOLD-signalchanges in fmri.
unfortunately I have no experience in creating such a factorial model in
spm. therefore your explanation is a bit to difficult for me. if i could
ask you to have a quick look about what i did?
i tried the option “flexible factorial” at the specify the 2nd level.
I created 2 factors (the first “subject” with all the defaults, the
second “painscore” as my covariate I want to test between the two groups).
At “specifiy subjects or all scans & factors” I gave in “specify all”,
specified the con-files of each of my participants (patients and controls)
and specified the factor matrix as “1 1 1 … 2 2 2 ….” (which is 1 for
patients and 2 for controls in the way I entered the scans, which I think
is totally wrong as a factor matrix).
now at this step I am absolutely to stupid to go ahead. I dont know what to
specify at “main effects & interactions”. I also wonder where I should give
information about the values of my second factor “painscore”. probably I
was wrong at this step too?
I am sorry to bother you and the spm list with such dumb questions. but I
am not familiar with matrices (even after reading “the joy of matrix maths”
which was no joy) and only rarely familiar with the mathematical background
of factorial designs.
if my question is to stupid, is there an “understandable” paper about
factorial designs in spm?
thanks in advance
markus
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