Hi Steven,
On 27 Mar 2007, at 11:08, Steven Platek wrote:
> Hi,
>
> Am fairly new to FSL and trying to use it to analyze some newly
> collected data.
> I have 17 subjects who all saw 4 different types of faces in an
> event-related fashion.
> There are two classes of face that each have two levels.
>
> Thus, I think I want to use the web example for a 1 X 4 repeated
> measures ANOVA, although it would also be nice to look
> at the 2 X 2 ANOVA and its interaction.
>
> I think I understand the description of higher level analyses on
> the website, but my question is
> what images/directories do I enter from first level? At the first
> level I computed contrasts for most permutations including each
> face class vs. null. So at level one for each subject I have feat
> directories including all contrasts and corresponding cope images for
> face 1 v null
> face 2 v null
> face 3 v null
> face 4 v null
> ...as well as contrasts for each face v each other face, etc.
Yes, these 4 contrasts are probably what you want to be passing up.
For many designs you would not need to be selecting each individual
contrast for each individual subject when setting up the higher-level
inputs, but you do in this case. Note that you should be able to use
the "Paste" button and an appropriate terminal command to get the
full list if you know Unix, something like:
echo /usr/people/platek/data/subject*/firstlevel.feat/stats/cope
{1,2,3,4}.nii.gz
> If I wanted to do the 1 X 4 ANOVA do I make a design matrix
> that looks like:
> EV1 EV2 EV3 .... EV17
> Input 1 1 0 0 ... 0
> Input 2 0 1 0 ... 0
> ...
> Input 17 0 0 0 ... 1
>
> (Each of the above indicate a subject in the analysis, correct?)
> ...
> Input 68
>
> The remainder EVs are EV18, 19, 20, & 21 which indicate each of the
> 4 levels of face stimuli, correct?
I think this is nearly right - if you look at
http://www.fmrib.ox.ac.uk/fsl/feat5/
detail.html#ANOVA1factor4levelsRepeatedMeasures
The first 2 EVs in this example are equivalent to your first 17, i.e.
remove the subject means and therefore turn these into repeated
measure tests. So that's good.
EVs 3-5 in the example are the important cell modelling and so you
want the same thing - i.e. you actually leave the 4th level out and
do an f-test across the other 3.
Note that if you also try the 2x2 example you'll replace EV4 with
your 17 subject mean EVs.
Cheers, Steve.
>
> Then my question is, since I have so many contrasts embedded in my
> first level feat directories, can I enter the cope images that
> correspond to each
> face stimuli class v null for the 4 levels of analysis in my design?
>
> Thanks in advance for helping me clear things up.
>
> Cheers,
> Steve
>
> ---
> Steven M. Platek, Ph.D.
> Associate and Managing Editor:
> Evolutionary Psychology
>
> Lecturer in Evolutionary Psychology
> School of Biological Sciences
> The University of Liverpool
> Liverpool
> L69 7ZB
>
> +44 (0) 151 795 4517
> +44 (0) 151 795 4408
> [log in to unmask]
>
> http://www.liv.ac.uk/evolpsyc/platek.html
> http://pcwww.liv.ac.uk/~splatek/
>
------------------------------------------------------------------------
---
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
------------------------------------------------------------------------
---
