Dear list,
I posted this message about a week ago, but got no answer. I wonder if
any of the SPM wizards is willing to comment on this issue.
Thanks a lot.
Jan
----- Forwarded message from Jan Gläscher <[log in to unmask]> -----
From: Jan Gläscher <[log in to unmask]>
To: [log in to unmask]
Subject: confused about effects of interest contrast weights
Dear Will, Karl and others,
I have encountered a contrast weight matrix in the standard 'effects of
interest' F-contrast at the 2nd level (different ANOVAs) that I cannot
explain.
I had expected an identity matrix as contrast weights, however the
actual values in SPM.xCon(1).c are actually quite dissimilar. In
addition, the same scaling effect of the contrasts weights occurs when
I specify an F-contrast via 'columns for reduced design' in the contrast
manager. In fact, when I try so specify an identity matrix
[eye(size(SPM.xX.X,2))] then this is not a valid contrast.
Could somebody explain this scaling of contrast weights to me? Does it
have to do with the non-sphericity correction?
Thanks a lot for your insights,
Jan
--
Jan Gläscher Neuroimage Nord
+49-40-42803-7890 (office) Dept. of Neurology, Bldg S10
+49-40-42803-9955 (fax) University Hospital Hamburg-Eppendorf
[log in to unmask] Martinistr. 52
20246 Hamburg
Germany
http://www.uke.uni-hamburg.de/zentren/neuro/neurologie/mitarbeiter/glaescher_jan.html
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