To compare groups you need to run a "Higher-level analysis" in FEAT
using the lower-level FEAT directories as inputs. This will then create
a group contrast for each of your lower-level copes. Assuming that you
have already created the desired lower-level copes at the individual
level, then no, you don't have to rerun individuals.
cheers,
-MH
On Tue, 2011-09-20 at 11:38 -0400, Leslie Engineering wrote:
> Or can I just treat them as two separate groups so i don't have to
> rerun individuals?
>
> On Tue, Sep 20, 2011 at 11:36 AM, Leslie Engineering
> <[log in to unmask]> wrote:
> So I am a little confused, then. If i have individual subjects
> that were run with two EVs contrasts (1,0) (0,1) (1,1), do I
> have to go back and rerun each individual subject with
> contrasts (1,-1)(-1,1) in order to get group differences or
> can I manipulate these in some way?
>
> On Tue, Sep 20, 2011 at 11:14 AM, Michael Harms
> <[log in to unmask]> wrote:
> Group contrasts (and statistics) should be calculated
> from the
> appropriate copes, not done "post-hoc" by subtracting
> z-maps.
>
> See
> http://www.fmrib.ox.ac.uk/fsl/feat5/detail.html#UnpairedTwoGroupDifference
> which provides a clear example of how to proceed.
>
> cheers,
> -MH
>
>
> On Tue, 2011-09-20 at 11:07 -0400, Leslie Engineering
> wrote:
> > does it make a difference if instead I have one
> group that went
> > through a single paradigm, EV. If EV is made up of
> two separate
> > stimuli blocks and I want to separate them into EV1
> and EV2, can I
> > run a single group average using EV1 and a single
> group average using
> > EV2 then subtract the z scores for an activation
> difference between
> > the two stimuli?
> >
> >
> > thanks so much
> >
> > On Tue, Sep 20, 2011 at 10:08 AM, Leslie Engineering
> > <[log in to unmask]> wrote:
> > Hello-
> >
> >
> > I ran two separate simple group average
> analysis. Both groups
> > underwent the same fmri scan sequence.
> Instead of rerunning a
> > group analysis and included all subjects
> from both groups and
> > setting up contrasts for group differences
> (1,-1)(-1,1), is it
> > statistically sound to simply subtract their
> zscores?
> >
> >
> >
> >
> >
> >
>
>
>
>
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