Hi,
this is the response your email got last time
> Hi - what was the error message?
>
> If your task C is filling up the "gaps" - is is in effect the
> baseline, then you should exclude this, if this is a first-level
> analysis, as the data and EVs all get demeaned at first level.
>
> Cheers, Steve.
>
For further clarification: for first-level analysis feat de-means all
the data. The implication is that your EVs only need to model signals
over and above the mean baseline signal C, i.e your design only needs
A and B.
A [1 0] contrast then is the 'where is signal under A > signal under
C' contrast and similarly for B.
A [1 -1] contrast test for A>B.
hope this helps
christian
On 3 Jul 2006, at 21:47, Joongnam Yang wrote:
> Hi all,
>
> I posted this question, but didn't get any response.
>
> I have three conditions, which are two tasks (A, B) and one control
> (C).
> I wanted to compare A vs. B, A vs. C, B vs. C.
> I came up with three design files for each condition, and did a
> contrast, say A vs. B, but FSL gave me an error.
> But I found out that if you load only two design files for A and B
> conditions, then A vs. B contrast was allowed to go.
>
> I don't understand what's going on with FSL model design.
> Would you someone clarify on this?
>
> Thanks in advance.
>
> Nam.
--
Christian F. Beckmann
Oxford University Centre for Functional
Magnetic Resonance Imaging of the Brain,
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
Email: [log in to unmask] - http://www.fmrib.ox.ac.uk/~beckmann/
Phone: +44(0)1865 222551 Fax: +44(0)1865 222717
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