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  

|
March 20, 2006 05:10PM
> 2 sample t-test can take care the unequal sample size issue. but
> then do we have to be carefully choosing a proper "error term" since
> we are now looking at each 2nd order contrast independently?


No, you don't make decision on the error term, 3dttest does it for you: It is a pooled error.

> correct me if i am wrong. for a three-factor type 5 design,
> BXC(A), in 3dANOVA3, the error terms for the 2nd order
> contrasts are the followings:
>
> factorB@levelA1 has an error term of MSBC(A)
> factorB@levelA2 also has an error term of MSBC(A)
>
> factorA@levelB1 has an error term of the pooled variance of MSBC(A) and MSC(A)
> factorA@levelB2 also has an error term of the pooled variance of MSBC(A) and MSC(A)


Well, it used to be the case (and that was exactly the reason why 3dANVA2/3 were vulnerbable to sphercity violation), but with the most recent modificaitons, the error terms in 3dANOVA2/3 are basically aligned up with the same ones used in one-sample or two-sample t test.

> I am not too sure if the 2 sample t-test will be able to give me
> reasonable results because of the error issue that I am concerned
> about.


Reasonable or not is in the eye of the beholder, I guess.

As long as there are enough number of subjects in each group, and the imbalance between the two groups is not too severe, I would worry it too much.

Gang
Subject Author Posted

2nd order contrast for the matlab GroupAna.m script

Ricky Tong March 10, 2006 10:06AM

Re: 2nd order contrast for the matlab GroupAna.m script

rick reynolds March 10, 2006 12:16PM

Re: 2nd order contrast for the matlab GroupAna.m script

Stacia Friedman-Hill March 10, 2006 12:44PM

Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 10, 2006 01:40PM

Re: 2nd order contrast for the matlab GroupAna.m script

Stacia Friedman-Hill March 10, 2006 03:38PM

Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 10, 2006 04:20PM

Re: 2nd order contrast for the matlab GroupAna.m script

Stacia Friedman-Hill March 13, 2006 10:16AM

Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 13, 2006 10:55AM

Re: 2nd order contrast for the matlab GroupAna.m script

Stacia Friedman-Hill March 13, 2006 11:35AM

Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 13, 2006 04:33PM

Found the problem - Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 13, 2006 05:44PM

Re: Found the problem - Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 13, 2006 09:39PM

Re: Found the problem - Re: 2nd order contrast for the matlab GroupAna.m script

Stacia Friedman-Hill March 14, 2006 01:53PM

Re: Found the problem - Re: 2nd order contrast for the matlab GroupAna.m script

Stacia Friedman-Hill March 14, 2006 04:04PM

Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 10, 2006 01:37PM

Re: 2nd order contrast for the matlab GroupAna.m script

Ricky Tong March 13, 2006 09:56AM

Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 13, 2006 11:02AM

Re: 2nd order contrast for the matlab GroupAna.m script

Ricky Tong March 13, 2006 11:20AM

Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 13, 2006 04:35PM

Re: 2nd order contrast for the matlab GroupAna.m script

Ricky Tong March 14, 2006 10:18AM

Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 16, 2006 02:18PM

Re: 2nd order contrast for the matlab GroupAna.m script

ye March 16, 2006 10:57AM

Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 16, 2006 02:26PM

Re: 2nd order contrast for the matlab GroupAna.m script

ye March 16, 2006 03:16PM

Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 16, 2006 05:50PM

Better solution - Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 17, 2006 03:05PM

Re: Better solution - Re: 2nd order contrast for the matlab GroupAna.m script

Ricky Tong March 20, 2006 04:40PM

Re: Better solution - Re: 2nd order contrast for the matlab GroupAna.m script

Gang Chen March 20, 2006 05:10PM