Dear statistics experts:
Basic question:
If I have conditions A and B and want to compare both with condition C
(design matrix: [A B C]; each condition with equal trial number) in an fMRI
experiment, a common procedure would be to use contrast [1 1 -2].
What does the "double weighting" of condition C do to it? Does this
contrast merely multiply beta values by -2, or does it multiply the trial
number of condition C by -2 and thus artificially reduce the variance? Is
this a problem for the statistical inference?
Is there any literature specifically dealing with this topic?
Thanks in advance
Juraj
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