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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Emperor Zhark
June 09, 2014 09:23AM
Please read the help section for 3dttest++ titled HOW COVARIATES WORK -- that explains exactly what is going on.

If you use the default centering option '-center DIFF' for a 2 sample test, then
#0 SetA-SetB_mean = difference of means [covariates removed]
will just truly be the difference of sample means (at each voxel). However, different options for centering will alter the "mean" results, since the "mean" values are then calculated by linear regression of the data samples w.r.t. the covariate(s) and then projected to the chosen covariate center.

If you are using covariates AND are using a 2 sample test, you should read the section
***** CENTERING (this subject is very important -- read and think!) *******
because it in fact is very important.
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Subject Author Posted

3dttest++ output

leslie999 June 06, 2014 03:39PM

Re: 3dttest++ output

rick reynolds June 06, 2014 04:09PM

Re: 3dttest++ output

Emperor Zhark June 09, 2014 09:23AM