Dear Mark,
Your contrasts have been changed because they are not estimable as
specified. This is because you have already modeled the difference
between cond 1 in group 1 and cond 1 in group 2 in terms of subject-
specific confounds. To look at group differences simply add all the
scans from one subject together and compare the two groups.
I hope this helps - Karl
----- Begin Included Message -----
>From [log in to unmask] Tue Apr 27 17:19:18 1999
Date: Tue, 27 Apr 1999 17:05:18 +0100
Reply-To: [log in to unmask]
X-Accept-Language: en-GB,en,en-US
Subject: contrasts
From: Mark Daglish <[log in to unmask]>
To: spm mailbase <[log in to unmask]>
X-Unsub: To leave, send text 'leave spm' to [log in to unmask]
X-List-Unsubscribe: <mailto:[log in to unmask]>
Dear "SPMers",
I am running a study where 2 groups of subjects undergo 6 scans in each
of 2 conditions. One of the contrasts I wish to look at is differences
between the 2 groups irrespective on the condition. I have entered the
study as "multi-study, with replications" with 2 groups and 2 conditions
in each group.
I enetered the following contrst matrix:
Contrast: 1 2 3 4 5 6 7 8 9 10 11 12
13 14
1 -1 1 -1 -1 1 -1 1 0 0 0 0
-1 1
-1 1 1 -1 1 -1 1 -1 0 0 -1 1
0 0
-1 1 -1 1 -1 1 0 0 -1 1 0 0
1 -1
1 -1 -1 1 1 -1 0 0 1 -1 1 -1
0 0
However what appears on the F map page of the output is:
Contrast: 1 2 3 4 5 6 7 8 9 10 11 12
1 -1 -1 1 -1 1 0 0 0.5 -0.5 -0.5
0.5
-1 1 1 -1 1 -1 0 0 -0.5 0.5 0.5
-0.5
-1 1 -1 1 0 0 -1 1 -0.5 0.5 0.5
-0.5
1 -1 1 -1 0 0 1 -1 0.5 -0.5 -0.5
0.5
Explanations please. Am I trying to do something invalid? Do I re-run
the analysis as 2 groups with 1 condition?
Thanks for any help
Mark
----- End Included Message -----
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|