Hi,
On 8 Nov 2006, at 04:38, Soohyun Cho wrote:
> Hi,
>
> I have two questions about the contrast setup in feat and how feat
> corrects for multiple comparisons.
>
> 1. In the feat gui - stats tab - full model setup - contrasts,
> there is a small box to the left of each contrast listed.
> If I unclick this box for a certain contrast, will that contrast
> not be included in the analysis at all ? or is it just left out of
> the report.html even though it was included in the analysis?
See the bubble-help for these buttons - turning the contrast off here
just affects what appears in the web page report - this is so that
you can generate contrasts for us in f-tests without having to
include them in the web page report.
> 2. When correcting for multiple comparisons, does feat take into
> consideration the # of contrasts run as well as the # of
> independent voxels (or blobs)?
> If yes, does feat take into the # of contrasts that were turned off
> along with the ones that were turned on?
Good question - no, correcting for multiple contrasts is up to the
user. So for example if you feed 5 contrasts into one f-test and
don't look at the individual contrasts, then there's no need to
correct for multiple comparisons.
Cheers, Steve.
>
> Thank you for your help,
> Soohyun.
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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
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