Gabriel Go.Es. wrote: > > Thank you so much, Doug > > I've check at your update and saw that this contrast has to be /2, > wich I guess means 0.5 instead of one to keep the scale right? Yes. > > and the contrast for me, would be something like: > Let's suppose > group1_males > group1_females > group2_males > group2_females > group3_males > group3_females > for differences between males and females (males > females) > regreessing the efects of group would be: > [0.333 -0.333 0.333 -0.333 0.333 -0.333] Correct > differences between group1 & group 3 regressing the effects of gender: > [0.5 0.5 0 0 -0.5 -0.5] Correct > and the differences between males and females for a single group can be: > [1 -1 0 0 0 0] > am I right??? Yes > but I don't yet figure out how to set a difference from 0 in any of > the group means (to meassure the effect of group), nor the interaction > between group and gender, and that's because my model is not like the > one from the example, Try using [1 -1 -1 1 0 0] [1 0 0 0 -1 1]
This is a single matrix with two rows. The first row tests for an interaction between G1/2 and M/F. The second row tests for G1/3 and M/F. Note that you don't need a third row. > > > > > > > Date: Wed, 9 Mar 2011 14:52:37 -0500 > > From: gr...@nmr.mgh.harvard.edu > > To: gabriel...@hotmail.com > > CC: freesurfer@nmr.mgh.harvard.edu > > Subject: Re: [Freesurfer] glm question > > > > That contrast is wrong. I've updated this page with the correct contrast > > https://surfer.nmr.mgh.harvard.edu/fswiki/Fsgdf6G0V > > which is: > > > > |+1 -1 0 -1 +1 0| > > |+1 0 -1 -1 0 +1| > > > > This is an F-contrast (two rows). The first row looks for a difference > > between L and R for M and F (ie, a simple interaction between LR and > > MF). The second row looks for a difference between L and A for M and F. > > If either of these subcontrasts shows an effect, then there is an > > interaction. > > > > doug > > > > > > Gabriel Go.Es. wrote: > > > > > > Dear FreeSurfer experts, > > > > > > > > > > > > I'm doing some group analyses and I'm a little stocked with this: > > > > > > I have Six Groups (2 Factors, one with three levels and the other one > > > with two levels), and one covariate. I don't know the rule for > setting > > > the contrasts for an ANOVA and for the interaction between the two > > > factors regressing out the covariate. I've checked at the FS wiki and > > > found the following contrast for six groups (two factors) and zero > > > covariates. > > > > > > > > > > > > Contrast 6 gender-x-handedness.mtx (interaction between gender and > > > handedness) > > > > > > [0.333 -0.333 -0.333 0.333 0.000 0.000 0.000 0.000 0.000] > > > > > > [0.000 0.000 0.000 0.000 0.000 0.333 -0.333 -0.333 0.333] > > > > > > > > > > > > I don’t understand the rule that has been followed. > > > > > > Can any one help me with this? > > > > > > > > > > > > Bests, > > > > > > Gabriel > > > > > > > > > > > > > > > > > > > > > > ------------------------------------------------------------------------ > > > > > > _______________________________________________ > > > Freesurfer mailing list > > > 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 > > Phone Number: 617-724-2358 > > Fax: 617-726-7422 > > > > Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting > > FileDrop: www.nmr.mgh.harvard.edu/facility/filedrop/index.html > > > > > > > > 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 Phone Number: 617-724-2358 Fax: 617-726-7422 Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting FileDrop: www.nmr.mgh.harvard.edu/facility/filedrop/index.html _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
