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

History of AFNI updates  

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October 12, 2005 12:04PM
> When collapsing these two together using method 2, we
> are concerned that when assigning 1s to these two
> conditions, the 76% and 24% receive equal weighting
> when clearly more trials are contributing to the correct
> estimate.


Such an equal weighting does not invalid any percent signal change estimation or contrast testing. Instead the effect is mainly on the precision of coefficient and contrast estimation. Putting in words with more statistical flavors, with a ratio of correct : incorrect answers = 76%:24%, the signal averaging process in 3dDeconvolve would render the estimation for correct answers with less standard error than that for incorrect answers by a factor of sqrt(76/24) ~ 1.78. In other words, the estimation for correct answers is 1.78 times more precise.

Gang
Subject Author Posted

Collapsing conditions in matrix files

George Cheney October 07, 2005 02:10PM

Re: Collapsing conditions in matrix files

Gang Chen October 07, 2005 03:45PM

Re: Collapsing conditions in matrix files

George Cheney October 07, 2005 05:46PM

Re: Collapsing conditions in matrix files

debbie October 10, 2005 11:59AM

Re: Collapsing conditions in matrix files

Jim Eliassen October 10, 2005 12:28PM

Re: Collapsing conditions in matrix files

Gang Chen October 12, 2005 12:04PM