Dear Doug, If I only have two groups, does the statistical test reduce to a two-tail t-test?
Sorry, I meant to ask what the "default" contrast is, meaning what the contrast is when I specify no nuisance factor? Is there an official document where the QDEC setup is gone over systematically? Thank you very much! Sincerely, Ye On Mon, Aug 19, 2013 at 11:04 AM, Douglas N Greve <gr...@nmr.mgh.harvard.edu > wrote: > > -log10(p) which p is the pvalue for the statistical test. The color is > signed by the test. > > > > On 08/19/2013 11:19 AM, ye tian wrote: > >> Dear Doug, >> >> Would you please shine some light on what quantities are being plotted in >> those statistical maps of QDEC? Some linear combination of the columns of >> the design matrix? >> >> Also, what is the "default" design matrix? >> >> Thank you very much! >> >> Sincerely, >> Ye >> >> >> On Tue, Aug 13, 2013 at 11:45 PM, Douglas Greve < >> gr...@nmr.mgh.harvard.edu >> <mailto:gr...@nmr.mgh.harvard.**edu<gr...@nmr.mgh.harvard.edu>>> >> wrote: >> >> >> 1 and 3 are the same model. Calling a variable a nuisance factor >> is just a description. The model is actually >> y = age*meditation*b1 + meditation*b2 + err = y_hat + err >> >> doug >> >> >> On 8/13/13 6:12 PM, ye tian wrote: >> >>> Dear Freesurfers, >>> >>> I am studying cortical thickness as a function of age >>> (continuous) and meditation practice (categorical, level1=Normal, >>> level2=TM). I have three separate cases of qdec, regression1, >>> regression2 and regression3. >>> >>> Regression1: Discrete (Fixed Factor) = meditation; Continuous >>> (Covariate) = age >>> Regression2: Discrete (Fixed Factor) = meditation; >>> Regression3: Discrete (Fixed Factor) = meditation; Nuisance >>> Factor = age >>> >>> For the question "Does the average thickness differ between >>> Normal and TM?", Regression1 and Regression3 have identical >>> result, which is different from Regression2, i.e., (1 = 3 !=2 ). >>> May I infer from this result the following about qdec: >>> >>> 1) Regression1 and Regression3 both fit cortical thickness,y, to >>> the model >>> y = b0 + age*b1 + meditation*b2 + err = y_hat + err >>> Regression2 fits: >>> y = b0 + b2*meditation + err = y_hat + err >>> >>> 2) Some function of y_hat goes into the "average thickness", >>> hence the difference between 2 and the others. >>> >>> However, what role does "Nuisance Factor" play in this case? >>> >>> Thank you very much! >>> >>> Sincerely, >>> Ye >>> >>> >>> >>> >>> >>> ______________________________**_________________ >>> Freesurfer mailing list >>> Freesurfer@nmr.mgh.harvard.edu <mailto:freesur...@nmr.mgh.** >>> harvard.edu <Freesurfer@nmr.mgh.harvard.edu>> >>> >>> https://mail.nmr.mgh.harvard.**edu/mailman/listinfo/**freesurfer<https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer> >>> >> >> >> ______________________________**_________________ >> Freesurfer mailing list >> Freesurfer@nmr.mgh.harvard.edu <mailto:freesur...@nmr.mgh.** >> harvard.edu <Freesurfer@nmr.mgh.harvard.edu>> >> >> >> https://mail.nmr.mgh.harvard.**edu/mailman/listinfo/**freesurfer<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<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 > Phone Number: 617-724-2358 > Fax: 617-726-7422 > > Bugs: > surfer.nmr.mgh.harvard.edu/**fswiki/BugReporting<http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting> > FileDrop: > https://gate.nmr.mgh.harvard.**edu/filedrop2<https://gate.nmr.mgh.harvard.edu/filedrop2> > www.nmr.mgh.harvard.edu/**facility/filedrop/index.html<http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html> > Outgoing: ftp://surfer.nmr.mgh.harvard.**edu/transfer/outgoing/flat/** > greve/ <ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/> > >
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