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
September 02, 2003 11:55AM
Hi,

I just did a little bit mathematics and checked the relative magnitude of unpaired and paired T statistics. It seems to me that the paired T statistic could be greater or smaller than, or even equal to, the unpaired T, depending on the specific datasets.

Whether paired T should be used is based on an assumption that the two datasets are pairwise correlated. And if you check the mathematics, the difference between the two formulae exactly reflects the assumption: If the two datasets are positively linearly correlated, unpaired T value is smaller than the paired; if the two are negatively linearly correlated, unpaired T value is greater than the paired; if their covariance is zero, then the two statistics are equal.

Gang
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Subject Author Posted

repeated measures

Philippe Goldin September 01, 2003 08:10PM

Re: repeated measures

Gang Chen September 02, 2003 11:55AM