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Hi, Mike: Thanks. Could you please give me more details about how to add columns and set contrast for gender x group interaction? Best Regards Jiansong =============== Jiansong Xu, M.D., Ph.D. Dept. of Psychiatry Yale Medical School 2 Church St., Suite 215 New Haven, CT 06519 203-785-5306 [log in to unmask] On Dec 4, 2009, at 11:14 AM, Michael Harms wrote: > If you want to assess an interaction (e.g. between group and gender) > then you'll need to include columns in the design matrix that allow > for > modeling of the interaction. Your 2nd design matrix only permits > modeling main effects. > > cheers, > -Mike H. > > On Fri, 2009-12-04 at 11:00 -0500, Jiansong Xu wrote: >> Dear All: >> >> I know this issue has been discussed in the list, but I still have >> questions. >> >> I have 3 groups: A: control; B: patients 1; and C: patients 2. >> >> group A B C >> 1 1 0 0 >> 1 1 0 0 >> 1 1 0 0 >> 1 1 0 0 >> 1 1 0 0 >> 2 0 1 0 >> 2 0 1 0 >> 2 0 1 0 >> 2 0 1 0 >> 2 0 1 0 >> 3 0 0 1 >> 3 0 0 1 >> 3 0 0 1 >> 3 0 0 1 >> 3 0 0 1 >> >> (We have > 170 subjects totally) >> >> Contrast for t- and f- test >> >> A-B: 1 -1 0 >> B-A: -1 1 0 >> A-C: 1 0 -1 >> C-A: -1 0 1 >> B-C: 0 1 -1 >> C-B: 0 -1 1 >> A 1 0 0 F >> B 0 1 0 F >> C 0 0 1 F >> >> I run randomise with following options: >> >> randomise -i input -o output -m mask -d design.mat -t design.con -f >> design.fts -n 5000 -c 2.0 -F 2.0 -V >> >> I got 9 outputs. I know the first 6 is for the 6 t-tests specified in >> above Contrast. My question is: how to interpret the last three >> outputs? Which one is the result of the F test? >> >> I also want to assess if the FA of male and female patients show >> different changes relative to male and female controls, respectively. >> I made following changes for design: >> >> group A B C Gender (0 for females and 1 for males) >> 1 1 0 0 0 >> 1 1 0 0 0 >> 1 1 0 0 0 >> 1 1 0 0 1 >> 1 1 0 0 1 >> 2 0 1 0 0 >> 2 0 1 0 1 >> 2 0 1 0 1 >> 2 0 1 0 1 >> 2 0 1 0 1 >> 3 0 0 1 0 >> 3 0 0 1 0 >> 3 0 0 1 1 >> 3 0 0 1 1 >> 3 0 0 1 1 >> >> Question: How to set the contrast for assessing the interaction of >> gender and group on FA values? >> >> >> >> Best Regards >> >> Jiansong >> >> =============== >> Jiansong Xu, M.D., Ph.D. >> Dept. of Psychiatry >> Yale Medical School >> 2 Church St., Suite 215 >> New Haven, CT 06519 >> 203-785-5306 >> [log in to unmask]