Paul,
I would have thought that what you need is a non(!)-paired t-test -
ther's no natural pairing between your controls and patients, is
there? You'd need a paired test if you were to scan the _same_ person
multiple times, e.g. on drug vs. placebo. And yes, it seems to me
that you do want to model the overall mean of the population - you're
interested in differences over and above the mean effect, but you
also might want to look at the mean itself in a contrast, i.e. you
want to model mean separately.
hope this helps
Christian
On 20 Jul 2007, at 18:47, Paul Geha wrote:
> Hello,
>
> I am running a t-test with diffusion data using TBSS between
> patients and age and sex matched control. Can I set-up a paired t-
> test for TBSS? I think it should be different from the one we use
> in FSL for fucntional data; is there a need to regress out the mean
> of every subject? Or should I just use an unpaired T-test.
>
> Another question, when I run a covariate analysis using TBSS is the
> EV needed to model the mean still needed as in the functional data?
> thanks a lot
> Paul
>
>
>
>
> Paul Geha M.D.
> Northwestern University
> The Feinberg School of Medicine
> Department of Physiology M211
> 303 E. Chicago Ave.
> Chicago, IL 60611
> Tel:312-503 2886
> Fax: 312-503-5101
>
____
Christian F. Beckmann
University Research Lecturer
Oxford University Centre for Functional MRI of the Brain (FMRIB)
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK.
[log in to unmask] http://www.fmrib.ox.ac.uk/~beckmann
tel: +44 1865 222551 fax: +44 1865 222717
|