Max
I'm sure to follow you here - how did you code for the task? if it is
ones everywhere then it simply removes the mean and 0 1 0 tells you how
much variance the second column explains
if you mean that for each scan you have a task and it is always the
same then the model is fine ..
hope this helps
c
> Thanks Cyril.
>
> So if I understand correctly, then it is not necessary to explicitly
> include the task column (the 3rd column with 1s everywhere) as an
> effect of interest?
>
> If the contrast should be 0 1 0 and the first 0 is controlling for age
> then isn't the second 0 somehow removing variance associated with the
> task?
>
> Thanks,
> Max
>
> On Thu, Jul 23, 2009 at 4:38 AM, cyril pernet <[log in to unmask]
> <mailto:[log in to unmask]>> wrote:
>
> Max
>
> I am trying to figure out which set of contrast codes is
> correct to examine the effect illness while controlling for
> age. The order of the columns in the attached screen shots is
> age, illness and task.
>
> there are 3 columns only so suppose 1st is age, 2nd illness - the
> 3rd one has 1s everywhere, i.e. this is your constant (mean) -
> correct contrast is the 2nd one [0 1 0] showing the unique
> variance explained by illness, age effect being taken into account.
>
>
>
--
Dr Cyril Pernet,
fMRI Lead Researcher SINAPSE
SFC Brain Imaging Research Center
Division of Clinical Neurosciences
University of Edinburgh
Western General Hospital
Crewe Road
Edinburgh
EH4 2XU
Scotland, UK
[log in to unmask]
tel: +44(0)1315373661
http://www.sbirc.ed.ac.uk/cyril
http://www.sinapse.ac.uk/
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.
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