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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pbedard
April 25, 2014 03:01PM
Hello,

I am using 3dttest++ for a between group ttest with 14 subjects in each group.
But depending on how I write the script the degrees of freedom change which makes me think the t-test used was a paired or unpaired.

3dttest++ -prefix ../anova/ttest_AAA-BBB \
-setA AAA \
s1_A+tlrc \
..
s15_A+tlrc \
\
-setB BBB \
s1_B+tlrc \
..
s15_B+tlrc \

This results in df = 12, which is incorrect. But if I use :

3dttest++ -prefix ../anova/ttest_AAA-BBB4 \
-setA AAA \
s1 s1_A+tlrc \
..
s15 s15_A+tlrc \
\
-setB BBB \
s1 s1_B+tlrc \
..
s15 s15_B+tlrc \

Now I have df = 26.
I did not see anything in the help page about that strange behavior.
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3dttest++ strange output

pbedard April 25, 2014 03:01PM

Re: 3dttest++ strange output

Emperor Zhark April 25, 2014 04:47PM