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.edumailto: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 in http://surfer.nmr.mgh.harvard.edu/fswiki/Fsgdf4G1V, I post my 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 E-mail: _yung-jui.yang@yale.edu_mailto:_yung-jui.yang@yale.edu_
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-- Douglas N. Greve, Ph.D. MGH-NMR Center greve@nmr.mgh.harvard.edumailto:greve@nmr.mgh.harvard.edu Phone Number: 617-724-2358 Fax: 617-726-7422
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