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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RWCox
January 25, 2021 11:23AM
There are a few points that come to my mind.
  1. You only have 16 samples (since a paired test is equivalent to a 1-sample test using A-B as the inputs). The program allows that, but it is really too few for good statistics in the permutation/randomization. That may be one cause of your lack of results.
  2. Was any blurring applied to the data during the processing that lead to the 3dttest++ run? That is, if you used afni_proc.py, did you specify blurring in the time series analysis? I ask because the amount of blurring you use is very low (0 and 2 mm) -- if this is the only blurring ever applied, it is too small to show FMRI results in most cases.
  3. I would use a wider range of pthr values, for example 'pthr=0.01/0.001/19' to specify 19 thresholds evenly spaced from 0.01 to 0.001, with step size (0.01-0.001)/(19-1)=0.0005. Using a range of pthr values is the main point of ETAC, and is what I was thinking of when I developed the idea while hiking in the Grand Canyon.
  4. Although using multiple hpow values seemed like a good idea to me at the time, it doesn't actually seem to make much difference. I now usually just use 'hpow=2'

I hope this helps, and apologize for the delay. If you have any followup questions, please email me. (The homework is to somehow find my email address.)
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Subject Author Posted

ETAC output file interpretation

activatedvoxel October 22, 2020 01:41PM

Re: ETAC output file interpretation

RWCox November 02, 2020 09:49AM

Re: ETAC output file interpretation

activatedvoxel January 05, 2021 01:43PM

Re: ETAC output file interpretation

activatedvoxel January 22, 2021 09:20AM

Re: ETAC output file interpretation

RWCox January 25, 2021 11:23AM