Dear Experts,
Let me ask one simple question about fMRI Random Effects Analysis(SPM99).
I have 3 conditions, A, B, and Rest. I compared A and B for each subject,
specifying the t-contrast (1,-1), and obtained con_***.imgs. Then I tried to
perform a group analysis using random effects model. I selected "one sample
t test" from Basic Stats menu and selected the con_***.imgs. So far so good.
Then the program requested to specify contrasts again. My question is how to
specify this second level contrast and what it means. I assume that one
sample t-test refers to a significant test against the null hypothesis: the
populaton mean=0, so I guess that the second level contrast should be "1".
Is this correct? and If so, why should we specify it? (because I cannot
think of any other numbers. As long as one sample t test is concerned, it
must be always 1, isn't it? What does it mean when it is , say, -1?)
Thank you in advance.
Chikashi Michimata, Ph.D.
Cognitive Psychology Lab
Psychology Dept.
Sophia Univ.
Tokyo Japan
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