Perhaps the FSL documentation has some examples that you could
reference. If not, I suggest that you consult with your local
statistics expert.
cheers,
-MH
On Fri, 2009-12-04 at 11:26 -0500, Jiansong Xu wrote:
> 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]
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