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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anderk
March 06, 2014 02:52PM
Dear Gurus,

I am new to issues of collinearity and am hoping for sage advice. From reading the forums, I know to ignore correlations among polort terms, but I'm not sure what to make of moderate correlations among regressors of interest (see below). I'm learning that orthogonalizing correlated regressors may address this issue, but how might this be implemented in AFNI? Alternatively, how does one quantify whether collinearity is an issue in their data (i.e. to answer whether moderate correlation even matters?).

Thanks in advance!
Kevin



----------- correlation warnings -----------

Warnings regarding Correlation Matrix: X.xmat.1D

severity correlation cosine regressor pair
-------- ----------- ------ ----------------------------------------
medium: -0.508 0.000 ( 0 vs. 5) Run#1Pol#0 vs. Run#2Pol#0
medium: -0.505 0.000 ( 5 vs. 10) Run#2Pol#0 vs. Run#3Pol#0
medium: -0.487 0.000 ( 0 vs. 10) Run#1Pol#0 vs. Run#3Pol#0
medium: 0.435 0.475 (19 vs. 25) cue_miss_one#0 vs. fbkMISS_one#0
medium: 0.406 0.452 (20 vs. 26) cue_miss_five#0 vs. fbkMISS_five#0
medium: 0.406 0.467 (15 vs. 21) cue_hit_zero#0 vs. fbkHIT_zero#0
medium: 0.405 0.469 (16 vs. 22) cue_hit_one#0 vs. fbkHIT_one#0
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Subject Author Posted

Multicollinearity in regressors of interest

anderk March 06, 2014 02:52PM

Re: Multicollinearity in regressors of interest

rick reynolds March 07, 2014 01:39PM