Doug, sorry, I am not sure I can fully understand. Do you mean the results are weighted MORE toward groups with smaller sample sizes (than groups with larger sample sizes)?
-- Daniel (Yung-Jui) Yang, Ph.D. Postdoctoral Researcher Yale Child Study Center New Haven, CT Tel: (203) 737-5454 E-mail: yung-jui.y...@yale.edu On 2/18/14 2:13 PM, "Douglas N Greve" <gr...@nmr.mgh.harvard.edu<mailto:gr...@nmr.mgh.harvard.edu>> wrote: It will tend to weight smaller groups by a proportion greater than the number of subjects in the group. On 02/18/2014 01:58 PM, Yang, Daniel wrote: 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_<mailto:_yung-jui.yang@yale.edu_> On 2/18/14 1:30 PM, "Douglas N Greve" <gr...@nmr.mgh.harvard.edu<mailto:gr...@nmr.mgh.harvard.edu> <mailto:gr...@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_> <mailto:_yung-jui.yang@yale.edu_> _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu<mailto:Freesurfer@nmr.mgh.harvard.edu> <mailto:Freesurfer@nmr.mgh.harvard.edu> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@nmr.mgh.harvard.edu<mailto:gr...@nmr.mgh.harvard.edu> <mailto:gr...@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<mailto:Freesurfer@nmr.mgh.harvard.edu> <mailto: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. -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@nmr.mgh.harvard.edu<mailto:gr...@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<mailto:Freesurfer@nmr.mgh.harvard.edu> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
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