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
June 25, 2009 04:26PM
For each subject the residuals from the "list.of.normal.control.ERRTs.files+tlrc" is a time series, while the corresponding beta from that subject in "list.of.normal.control.fear.files+tlrc" would be just one number. If you try the following

3dttest -set1 `cat list.of.normal.control.ERRTs.files+tlrc` -set2 `cat list.of.normal.control.fear.files+tlrc` -prefix Controls.Fear_Versus_Errts

you will get the same result as your option 1 because each subject's residuals add up to 0 in this two-sample t-test.

> Our concern with using "-base1 0" is that wouldn't this t-test only identify
> voxels whose Coefficient are significant from 0, not neccessarliy different from
> a baseline (or fixed)?

Since the baseline is automatically added in the regression model (unless you explicitly turned it off with something like -polort -1 in 3dDeconvovle), each regression coefficient (beta) is indeed a contrast relative to the baseline by default.

Gang
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Subject Author Posted

One Group T-Test

BrianB June 25, 2009 10:21AM

Re: One Group T-Test

Gang Chen June 25, 2009 11:27AM

Re: One Group T-Test

BrianB June 25, 2009 03:10PM

Re: One Group T-Test

Gang Chen June 25, 2009 04:26PM