LLN, le 28/09/05
Dear Leandro,
>I have a basic question, let say I have tow conditions: activation
>and rest. (100 scans).
>Vector onsets for the activation condition is: 10 30 50 70 90. Duration: 10
>Vector onsets for the rest condition is: 20 40 60 80. Duration: 10
>
>Is it the same to specify only the activation condition (contrast
>[1]) than specifing both conditions (contrast [1 - 1])?
No, it's not the same:
- [1 -1] tests for positive differences between Activation and Rest;
- [1] tests for positive differences between Activation and
"Anything that is not declared", i.e., your scans 0 to 9 that are not
declared in your vectors.
Hope this helps,
Mauro.
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Mauro PESENTI
Research Associate, National Fund for Scientific Research (Belgium)
Unite de Neurosciences Cognitives
Departement de Psychologie
Universite Catholique de Louvain
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B-1348 Louvain-la-Neuve
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http://www.nesc.ucl.ac.be
http://www.nesc.ucl.ac.be/mp/pesentiHomepage.htm
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