On Friday 27 May 2005 09:41, Jean-Marc" "Esnault wrote:
> I begin using SPM and I can't understand why whit a single task (motor-
> rest), 56 dynamics (volumes), I observe 51 DF ???? I thought I would have
> found 54=56-2 DF
> Please, help me.
Hi Jean-Marc,
df depend on the number of volumes in the analysis (J) and the number of
regressors/columns in your design matrix (P), resulting in J-P df (using
Greenhouse-Geisser correction would lead to different results for df). Maybe
you measured 56 volumes, but the first 3 scans where excluded as usual? How
did you model the basline: explicit or implicit?
Cheers,
Thilo
--
Thilo Kellermann
RWTH Aachen University
Pauwelstr. 30
52074 Aachen
Tel.: +49 (0)241 / 8089977
Fax.: +49 (0)241 / 8082401
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