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>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 > listfreesur...@nmr.mgh.harvard.eduhttps://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > > _______________________________________________ > 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. > >
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