Hi Doug, Thanks for replying. Yet I have a question on this matrix. From what I see, each row corresponds to one contrast, which has one df. Thus why are we having 8 rows while the interaction has a df of 4?
Thanks, Cherry On Sun, Nov 18, 2012 at 6:23 PM, Douglas Greve <gr...@nmr.mgh.harvard.edu>wrote: > > Hi Bo, you can think of the Ftest as a logical 'OR' between the t-test > contrasts indicated in each row. Each row is a difference of differences, so > > 1. (A-B)om - (A-B)pm --> Does the difference between A and B differ > between groups O and P for Males? > 2. (A-B)om - (A-B)qm > 3. (A-C)om - (A-C)pm > 4. (A-C)om - (A-C)qm > 5. (A-B)of - (A-B)pf --> Does the difference between A and B differ > between groups O and P for Females? > 6. (A-B)of - (A-B)qf > 7. (A-C)of - (A-C)pf > 8. (A-C)of - (A-C)pf > > I've put together the first 9 columns of the first 4 rows. The last 9 > columns are all 0s. For the last for rows, the 0s and below matrix are > swapped to give you the same for the females > > doug > > AOM BOM APM BPM AQM BQM COM CPM > CQM > -------------------------------------------------------------------------- > +AOM -BOM -APM -BPM 0 0 0 0 > 0 > +AOM -BOM 0 0 -AQM +BQM 0 0 > 0 > +AOM 0 -APM 0 0 0 -COM +CPM > 0 > +AOM 0 0 0 -AQM -COM 0 > +CQM > > > > On 11/17/12 9:21 PM, xiangbo_2010 wrote: > > Hi Freesurfer experts,**** > > I'm very sorry to bother you, but I am very confused with the following > questions: > > My experimental design includes three discrete factors: factor > 1 with three levels (A,B,C ); factor 2 with three levels (O,P,Q); gender > (F, M), and one covariate. > > So I can get 18 classes: FAO, FAP,FAQ,FBO,FBP,FBQ,FCO,FCP,FCQ,MAO, > MAP,MAQ,MBO,MBP,MBQ,MCO,MCP,MCQ. I want to perform the interaction > between factor 1 and factor 2 regressing out the effect of gender and one > covariate, but I don't know the rules for setting the contrasts for the > F-test. The contrast matrix I used is: > > 1 1 1 -1 -1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > > 1 -1 0 1 -1 0 1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > > 1 1 1 0 0 0 -1 -1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > > 1 0 -1 1 0 -1 1 0 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 > > 0 0 0 0 0 0 0 0 0 1 1 1 -1 -1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 > > 0 0 0 0 0 0 0 0 0 1 -1 0 1 -1 0 1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 > > 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 -1 -1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 > > 0 0 0 0 0 0 0 0 0 1 0 -1 1 0 -1 1 0 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 > > is it correct? > > > > Any help will be very appreciated. > > > > Best wishes, > > > > Bo Xiang > > > > > > > > > > > _______________________________________________ > 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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