Dear all,
I have two groups: controls and schizophrenics. I used the canonical hrf +
the two derivatives in my model. I created the following contrasts for the
difference between A and B for each subject from each group:
[1 0 0 -1 0 0] canonical HRF A-B
[0 1 0 0 -1 0] temporal derivative A-B
[0 0 1 0 0 -1] dispersion derivative A-B
I was then able to examine the overall effect for _each group_ separately
using a one-way ANOVA (without constant term), modelling the three contrast
images as three groups using the F-contrast:
[1 0 0
0 1 0
0 0 1]
and also got the t-contrast for the HRF alone:
[1 0 0]
What if I want to compare the two groups now? Do I do a one-way ANOVA where
I enter six groups - one for each contrast for each group and then do an
F-contrast like:
[1 0 0 -1 0 0
0 1 0 0 -1 0
0 0 1 0 0 -1]
to get the overall effect?
Can I do an equivalent of the t-test above, such as:
[1 0 0 -1 0 0] to find A>B group 1>2?
Please advise. I understand what to do for one group but I am not sure how
to set this up correctly for between groups comparisons.
Thank you!
Martin
Martin Zalesak, M.Sc.
PhD Candidate in Medical Engineering
Harvard-MIT Division of Health Sciences and Technology
Admissions Building, Rm. # 347
McLean Hospital
115 Mill St.
Belmont, MA 02478
Phone: (617) 855-2961
Fax: (617) 855-2985
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