AFNI Message Board

Dear AFNI users-

We are very pleased to announce that the new AFNI Message Board framework is up! Please join us at:

https://discuss.afni.nimh.nih.gov

Existing user accounts have been migrated, so returning users can login by requesting a password reset. New users can create accounts, as well, through a standard account creation process. Please note that these setup emails might initially go to spam folders (esp. for NIH users!), so please check those locations in the beginning.

The current Message Board discussion threads have been migrated to the new framework. The current Message Board will remain visible, but read-only, for a little while.

Sincerely, AFNI HQ

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Gang Chen
January 12, 2005 04:31PM
> I’m trying to create an interaction map (A1 > A2) > (B1 >
> B2) that will show the direction of (positive and negative)
> effects.

It seems to me that a more straightforward way is to run 3-way ANOVA instead of 2-way.

> Can this be done using 3dANOVA2? For example,
> using 3dANOVA2, I can produce separate maps with
> direction by labeling the 2 X 2 design as 4 conditions
> (A-D), and creating the contrast for A > B using –acontr 1
> -1 0 0, and for C > D using –acontr 0 0 1 -1. Given this,
> can I also specify (A > B) > (C > D)? If so, how?

If the 4 levels are A1 A2 B1 B2 in 2-way ANOVA, then the hypothesis "A1 = A2" (not A1 > A2) is 1 -1 0 0, and 0 0 1 -1 for "B1 = B2". For (A1 - A2) = (B1 - B2), it is 1 -1 -1 1. Then you can figure out the direction of each contrast based on the sign of either its intensity or t value.

Gang
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Subject Author Posted

3dANOVA2

Brian January 12, 2005 12:14PM

Re: 3dANOVA2

Gang Chen January 12, 2005 04:31PM

Re: 3dANOVA2

Brian January 12, 2005 05:31PM

Re: 3dANOVA2

Gang Chen January 12, 2005 05:38PM