Dear SPMers:
We have two groups of subject (patient and control) and scans twice in each
subject (before and after treatment). When we compared them using
"multigoup: conditions and covariates" in SPM2, we can compared the
treatment effect within group (i.e., before>after in patient group only),
and main effect of treatment (i.e., before>after in pool of the scans from
patient and control). However, when we try to test the main effect of group
(i.e., patient>control in pool of the scans from before and after
treatment), the contrast manager showed "invalid contrast" and refuse to
compare the main effect of group. Why this contrast is invalid? Can anyone
kindly explain the reason to me or point out the appropriate way to compare
them?
Thanks you very much.
Best regards
--
§ù¬F©þ
Cheng-Hao Tu, PhD Student
Laboratory of Integrated Brain Research
Department of Medical Research and Education
Taipei Veterans General Hospital
No.201, Sect.2, Shih-Pai Rd.
Taipei
Taiwan
Email: [log in to unmask] or [log in to unmask]
Tel: +886-2-28712121 ext 3474
Fax: +886-2-28745182
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