good morning,
I have a matrix with 2 groups, 15 subjects per group, same task.
there is one task variable and one baseline variable per subject.
to look at one group task (first column) minus baseline (second column), I'm putting in a contrast of
1 -1 1 -1 1 -1 ...for 15 subjects
no problem
for second group
0 0 0 0 0 ... for 15 subjects, then 1 -1 1 -1 1 -1 ...for 15 subjects
no problem.
now I'd like to look at strictly subtracting the task from group one minus the task from group 2 without doing a double subtraction (without subtracting baseline).
1 0 1 0 1 0....15subjects, -1 0 -1 0 -1 0.... 15 subjects
and I'm getting an invalid contrast error.
is this an invalid contrast and why?
if It's a machine thing, I'm using matlab
6.5, XP, SPM2
thanks you for any ideas.
sophie
--
Sophie Josee Lafaille, B.Sc.(Hons.), M.Sc.
Research Officer II, Speech Fluency Laboratory 1059
Department of Speech-Language Pathology, University of Toronto,
500 University Avenue, Rm 160, Toronto, Ontario, M5G 1V7
Phone: 416-946-8635 Fax:416-978-1596
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