Thanks Doug! One follow-up question: since it's [0.25  0.25  0.25  0.25], would the effect be biased toward large sample sizes in one of the groups (versus the other groups)?

Or, does FreeSurfer qdec take care of the unequal cell, in a possible way analogous to using Type III SS in the traditional ANOVA?

Best,
Daniel
-- 
Daniel (Yung-Jui) Yang, Ph.D.
Postdoctoral Researcher
Yale Child Study Center
New Haven, CT
Tel: (203) 737-5454
E-mail: yung-jui.yang@yale.edu

On 2/18/14 1:30 PM, "Douglas N Greve" <greve@nmr.mgh.harvard.edu> wrote:

That looks right to me
doug


On 02/18/2014 10:08 AM, Yang, Daniel wrote:
Dear FreeSurfer experts,

I have two binary factors (F1: F1L1 F1L2; F2: F2L1 F2L2), 1 covariate
(COV), and 1 nuisance factor (NUI). I want to make sense of some
specification of the regressors and contrasts.
Because they are not described
understanding below. Can you let me know if it is correct?

This model using the DODS method will have 12 regressors:

Regressor1: 1's for F1L1 F2L1, 0 otherwise (i.e., offset for Group 1)
Regressor2: 1's for F1L1 F2L2, 0 otherwise (i.e, offset for Group 2)
Regressor3: 1's for F1L2 F2L1, 0 otherwise (i.e., offset for Group 3)
Regressor4: 1's for F1L2 F2L2, 0 otherwise (i.e., offset for Group 4)
Regressor5: COV for Group1 subjects, 0 otherwise (i.e., COV slope for
Group 1)
Regressor6: COV for Group2 subjects, 0 otherwise (i.e., COV slope for
Group 2)
Regressor7: COV for Group3 subjects, 0 otherwise (i.e., COV slope for
Group 3)
Regressor8: COV for Group4 subjects, 0 otherwise (i.e., COV slope for
Group 4)
Regressor9: NUI for Group1 subjects, 0 otherwise (i.e., NUI slope for
Group 1)
Regressor10: NUI for Group2 subjects, 0 otherwise (i.e., NUI slope for
Group 2)
Regressor11: NUI for Group3 subjects, 0 otherwise (i.e., NUI slope for
Group 3)
Regressor12: NUI for Group4 subjects, 0 otherwise (i.e., NUI slope for
Group 4)

Description1: Does the correlation between thickness and COV,
accounting for F1 and F2, differ from 0? Nuisance factors: NUI
Contrast1: [0  0  0  0  0.25  0.25  0.25  0.25  0  0  0  0]

Best,
Daniel

--
Daniel (Yung-Jui) Yang, Ph.D.
Postdoctoral Researcher
Yale Child Study Center
New Haven, CT
Tel: (203) 737-5454


_______________________________________________
Freesurfer mailing list

--
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
Phone Number: 617-724-2358
Fax: 617-726-7422

Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting
FileDrop: https://gate.nmr.mgh.harvard.edu/filedrop2
www.nmr.mgh.harvard.edu/facility/filedrop/index.html
Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/

_______________________________________________
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer


The information in this e-mail is intended only for the person to whom it is
addressed. If you believe this e-mail was sent to you in error and the e-mail
contains patient information, please contact the Partners Compliance HelpLine at
http://www.partners.org/complianceline . If the e-mail was sent to you in error
but does not contain patient information, please contact the sender and properly
dispose of the e-mail.