Dear SPM ers;
I have some questions regarding the confusion due to reading so many
responses in the archives.
I have 5 conditions in my study with two groups of old and young people.
Thanks God that I'm not interested in comparing all conditions, therefore
in the first level I built a contrast let's say condition 2-baseline (0 1 0
0 -1)=A and condition 4 - baseline (0 0 0 1 -1)=B
Then in group level I used these contrasts to compare between young and
old in full factorial design, because I want to see the interaction. So,
here are my questions:
1. Is the way of defining my first level contrasts correct or should I use
Imcalc? the results are different.
2. why in second level analysis some people build contrast like 1 0, the
sum of contrast should be equal to zero, does it depend to the hypothesis
or it is a rule?
3. in full factorial condition, I'm interested to see if old group showed
greater activation than young group, should I use t-test instead of F-test?
the results are different as well (as one would expect).
4. IF I wanna use the contrasts A and B to see where are the common areas
in those condition across groups, should I use conjunction analysis, if
yes, if conjunction analysis is the same as using inclusive mask?
The responses would be appreciated alot
--
**********************
Maryam Ziaei
PhD Student
Department of Psychology (Cognitive Science)
Stockholm University
Tel: +46-8-163845
Fax: +46-8-159342
Alternative Email: [log in to unmask]
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