Dear Lords of FSL,
I have a simple question re the contents of the PE and COPE images.
At a first level (single sub - single run) PE1 is a matrix containing
the GLM parameter estimate (b) for each voxel for EV1. If I created a
contrast with (say) a 1 in EV1 and zeros in all other EVs I would then
get COPE1 to be in fact the same thing as PE1 except it's a beta as
opposed to a non standardized estimate (i.e. b). [the betas are what I
need..]
So far so good (right? ..I think we previously discussed this already..)
Now, say that I have multiple runs and multiple subjects, and all I do
is average (i.e. no subtractions) EV1 across multiple sessions (for each
given subject) and across multiple subjects.
This group analysis will yield again a PE1 and a COPE1 (obtained again
just by creating a contrast with 1 in all EV1s and 0 for all other EVs).
Are the EP1 and COPE1 matrices just (group) average bs and (group)
average betas, respectively?
cheers
Martin
--
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"Upward, not Northward!" [Edwin Abbott - FlatLand]
I became insane, with long intervals of horrible sanity. [E.A. Poe]
Would you tell me, please, which way I ought to go from here? ''That depends a good deal on where you want to get to.'' Said the Cat. I don't much care where -- Said Alice. Then it doesn't matter which way you go, said the Cat. [Lewis Carroll]
Che si trattasse di una gara? ..Un colpo il mondo e un colpo tu, a chi stupiva un po' di piu'.. [Per Un Vecchio Bambino - Roberto Vecchioni]
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Martin M. Monti
Princeton University
Department of Psychology
Green Hall 3-S-8
(609) 258-5679
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