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

History of AFNI updates  

Previous Message Next Message
Message List New Topic Print View
|
gang
November 16, 2019 05:41PM
Sanaz,

> the term 'removed' in [covariates removed] means that the covariate is controlled for in this comparison.

You're correct that the description in the 3dttest++ help can be improved.

You seem to have a 2 x 2 data structure. If you decide to use 3dttest++ instead of 3dMVM to handle the situation, there are a couple of subtleties involved. One, it sounds like you're going to ignore the interaction effect. Two, dummy coding a categorical variable can be tricky. For example, 0/1 coding for sex could cause some unwanted side effect, If you really want to use 3dttest++,

1) make sure the assumption of no interaction is reasonable
2) code the two sexes with something -0.5 and 0.5 (or -1 and 1). See more details here: [stats.idre.ucla.edu]

Gang
Reply Quote
RSS
Subject Author Posted

3dttest++

Sanaz_khosravani November 14, 2019 12:35PM

Re: 3dttest++

Sanaz_khosravani November 14, 2019 02:32PM

Re: 3dttest++

gang November 16, 2019 05:41PM

Re: 3dttest++

Sanaz_khosravani November 18, 2019 09:56AM