Hi Dorian,
Dorian P. wrote:
> Jan, I didn't catch very well the idea. Are you proposing to split the
> actual trials in different conditions?
> This would be problematic. I have a memory experiment with 5 levels.
> In one parametric modulation I want to catch 1-2-3-4-5. In another one
> I want to leave out "5" and catch 1-2-3-4 only. I cannot catch the
> first pmod if I split level 5 to another condition. Finding a way to
> exclude trials can be very useful to try modulations in different
> ways, i.e. all response levels, or with only correct responses, etc.
I am not aware that you can actually do that in the same analysis. You
could setup two different GLMs though, one with all trials included, and
another one with just the frist four memory levels. Or else, you could go
back to a "categorical" design and model all memory levels in different
conditions (without parametric modulations) and use your contrast to test
for the increase (linear or otherwise) across either 4 and 5 memory levels.
Cheers,
Jan
--
Jan Gläscher, Ph.D. Div. Humanities & Social Sciences
+1 (626) 395-3898 (office) Caltech, Broad Center, M/C 114-96
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