> We are analyzing VBM data using spm02.
>
> spm99 analysis allowed the entry of more than 1 nuisance variable if
> certain design types were chosen (for ex, Population main effects 2 cond 1
> scan/cond or.. Multi group 2 cond, etc...). In spm02 it appears as if
> only one nuisance variable can be put in the design matrix.
>
> We are using Ancova as a design type. Should we use some other design that
> will allow us to enter 2 nuisance variables?
As far as I know, I don't think it makes a great deal of difference (for
VBM studies), whether or not a covariate is considered to be a confound
or not, unless you do any non-sphericity correction, in which case it
may matter. How the covariates are treated will depend on your contrasts.
Best regards,
-John
--
Dr John Ashburner.
Functional Imaging Lab., 12 Queen Square, London WC1N 3BG, UK.
tel: +44 (0)20 78337491 or +44 (0)20 78373611 x4381
fax: +44 (0)20 78131420 http://www.fil.ion.ucl.ac.uk/~john
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