Steve,
Thanks for the reply. I am pretty sure I am using the newest version. I am using Randomise version 2.1 which came with FSL version 4.1.
Please let me know if there is a newer version of FSL out there that I do not know about.
Thanks.
Lindsay.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf Of Steve Smith
Sent: Wednesday, August 26, 2009 1:34 AM
To: [log in to unmask]
Subject: Re: [FSL] Randomise TFCE paired t-test biased results?
Hi - the first thing I would do is install the latest version of FSL -
you are using quite an old randomise, and the way that multiple
covariates are handled has improved over various versions. You won't
need to change any of the preprocessing - just install the latest FSL
and use the version of randomise in that.
Cheers.
On 25 Aug 2009, at 19:37, Lindsay Walker wrote:
> I am using Randomise with the TFCE function (using version Randomise
> version
> 2.1) to do a paired t-test, where my two groups are the same set of
> subjects
> processed in two different ways. We want to see the voxel wise
> differences
> between these two processing methods. I am running this on whole
> brain
> anisotropy maps which have been scaled to values between 0 and
> 1000. I
> used the -T option for TFCE, not the --T2, as I am interested in whole
> brain, and did not run TBSS on my data. I can provide my design
> matrix if
> that might help explain things.
>
> The results are somewhat concerning, in that it appears that
> Randomise is
> picking up on negative differences, but not positive differences.
> In other
> words, there are significant differences in the tfce_corrp_tstat2
> file, but
> none in the tfce_corrp_tstat1 file. While qualitatively in our data
> we see
> some positive and some negative differences. We are, therefore,
> concerned
> that the results are biased in some way.
>
> Has anyone else experienced anything like this?
>
> Lindsay Walker.
>
---------------------------------------------------------------------------
Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
---------------------------------------------------------------------------
|