On Nov 12, 2009, at 9:38 AM, Jesper Andersson wrote:
> That means that in FSL the recommended way to analyze the two-
> factorial experiment I alluded to above is to create the relevant [1
> -1 -1 1] contrast for each subject at the first level and then pass
> that (along with the uncertainty of that estimate) up to the second
> level and there simply do a one sample t-test.
>
> I hope this has answered your question?
I believe so.
The one thing that still seems to be a bit of an issue is whether I
can correct for multiple contrasts, for example, if I have 1 contrast
of interest, or 2 or 100 (in theory only!). If I do higher-level
contrasts independently for just 1 contrast vs. 100, I am nearly
guaranteed to get spurious significance in the latter case. In my
case, I have a handful of contrasts (which are actually largely
independent - along the lines of modelling 3 two-level factors and the
interactions between them). Thus, I am still a little concerned about
correcting for these multiple (but at least partially independent)
contrasts.
Or is this handled already by those contrasts having been specified
simultaneously at the first two levels?
Cheers,
Dav
|