Hi Andrew,
>If each run is analysed separately, do I combine them as if they are
>separate subjects doing the experiment or is there a different method in
>this case?
Well, you could either. The first method -- combining them as if they were
separate subjects, is what SPM does. You can do the same in Feat by
choosing a group stats analysis and entering each session into the whole.
Alternatively you could manually create mean contrast of parameter estimate
(COPE) images per subject and then use Medx to compute a group random
effects analysis form the subjects' mean PE files. I've attached a script
I've used to do this method, again in ksh. This one isn't commented as
much and could be made more elegant but it follows the same pattern.
Once you have the mean images per subject (in standard space), you need to
load them into a group in medx and choose Toolbox -> Functional -> Group
Statistics. Then set the operation to single group t-test and run it on
your grouped COPE images. I'm not sure how to script this part from within
the rfx shell script so I do it manually. Afterwards, if you save the
z-image, you can run a second script called thresh_render (attached) to
make the various images that you normally get from Feat.
This isn't completely elegant but it does compute a type of repeated
measures RFX analysis which is more correct that simply treating the
various runs as different subjects.
Perhaps one of the more statistically-minded members of the list will
comment on that.
Cheers,
Joe
Joe
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