Dear list,
We have problems with creating T-contrasts in my design. I would appreciate any kind of help We receive...
1))) My conceptual design is the following one:
|--Day 0: 9 images (1 image per subject)
|--- VH (9 subjects) --- |
| |--Day 2: 9 images (1 image per subject and same subjects as Day 0)
|-- Female----|
| | |--Day 0: 8 images (1 image per subject)
| |--- CP (8 subjects) --- |
| |--Day 2: 8 images (1 image per subject and same subjects as Day 0)
|
--|
| |--Day 0: 6 images (1 image per subject)
| |--- VH (6 subjects) --- |
| | |--Day 2: 6 images (1 image per subject and same subjects as Day 0)
|---- Male ---|
| |--Day 0: 7 images (1 image per subject)
|--- CP (7 subjects) --- |
|--Day 2: 7 images (1 image per subject and same subjects as Day 0)
2))) In SPM5, we choose Flexible Factorial and 3 factors in the following order: subject, group (for levels VH and CP), replication (for levels Day 0 and Day 2) and sex (for levels female and male).
Subject: Independent Yes and Variance Equal
Group: Independent Yes and Variance UnEqual
Replication: Independent No and Variance UnEqual
Sex: Independent Yes and Variance UnEqual
For example, for the two images (day 0 and day 2) of subject female VH, its conditions are: 1 1 1; 1 2 1;
For example, for the two images (day 0 and day 2) of subject female CP, its conditions are: 2 1 1; 2 2 1;
For example, for the two images (day 0 and day 2) of subject male VH, its conditions are: 1 1 2; 1 2 2;
For example, for the two images (day 0 and day 2) of subject male CP, its conditions are: 2 1 2; 2 2 2;
3))) The main effects and interactions are:
Main effect: subject (1)
Interactions: group and replication (2 and 3); group and sex (2 and 4)
4))) We want to test main effect in sex (FEMALE>MALE)
We tried with the t-contrasts: zeros(1,38) 1 1 -1 -1
1/17*ones(1,17) -1/13*ones(1,13) zeros(8) 1 1 -1 -1
and they doesn´t work..., why?
Regards
Veronica
my design is as follows:
2 groups (N1, N2), 2 conditions (C1, C2). i specified 3 factors (subject,
group, condition) and got a design matrix comparable to darrens and matts
one (see attached file). the first 26 columns are for the subjects, the
last 4 columns are for the factor interactions (N1xC1, N1xC2, N2xC1, N2xC2).
so i want to have the following contrasts, which i managed to specify in
spm.
my first question is:
are the following contrast definitions correct?
i read the discussion in the list about the 2x2 ANOVA with great interest,
because i like to setup a similiar design. so i followed the procedure of
darren and matt for the flexible factorial design setup.
i designed 3 factors (subject (2xn), group (2 groups), condition (2
conditions) /independence yes, yes, no / variance equal, unequal, unequal).
specified the design by subject. for each subject of my group 1 the
condition matrix is [1 1;1 2], for each subject of my group 2 [2 1;2 2].
There is a main effect of subject (factor number 1) and an interaction of
group x condition (factor numbers 2 3).
This produces a design very similiar to the ones of darren and matt. i got
n columns for my n participants, each with 2 rows. Now the difference and
my problem:
i got only 3 columns of group x condition instead of my expected 4. these
are column 1 (group1 x condition2), column 2 (group1 x condition2), and
column 3 (group2 x condition2). the lacking column (group2 x condition1)
seems to be mixed into column 2 (see attached file).
does anybody know what my mistake is?
thanks markus
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