yes, or do post hoc tests
doug

On 2/21/14 6:35 AM, Yang, Daniel wrote:
Thanks, Doug! I guess in order to interpret the interaction correctly, I would need to extract the thickness value and plot the interaction.

Best,
Daniel
 
-- 
Daniel (Yung-Jui) Yang, Ph.D.
Postdoctoral Researcher
Yale Child Study Center
New Haven, CT
Tel: (203) 737-5454
E-mail: yung-jui.yang@yale.edu

On 2/20/14 2:57 PM, "Douglas N Greve" <greve@nmr.mgh.harvard.edu> wrote:


The basic contrast is
(PM-PF)-(CM-CF)
If that is positive, then it will be red, otherwise blue

This opens up a lot of possibilities as to what is driving the
interaction, so it is hard to come up with a sentence like the one you
are trying to state

doug


On 02/20/2014 02:25 PM, Yang, Daniel wrote:
Dear FreeSurfers,

I have two discrete and binary factors (Dx: patients vs. controls;
Sex: female vs. male), one continuous variable (Age), one nuisance
factor (IQ). If there is a 3-way interaction of Dx x Sex x Age,
regressing out IQ, is the following interpretation correct?

Red/yellow: In females (vs. males), the Age effect of cortical
thickening is stronger in patients (vs. controls).
Blue/cyan: In females (vs. males), the Age effect of cortical thinning
is stronger in patients (vs. controls).

Note. by stronger, I mean greater magnitude without sign.

Thanks,
Daniel





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MGH-NMR Center
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