Yes, that -BPM should be +BPM, sorry about that. It will not change the p-values if you multiply by 0.5 or not. It will change the size of the contrast. Most people don't report this number, especially for an F-test, so I would not worry about it. doug
On 11/20/2012 09:17 AM, xiangbo_2010 wrote: > Dear doug > Thank you for your reply! > +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 > there should be use 1 -1 or 0.5 -0.5? whether the -BPM should be > change BPM? > Thanks > Bo Xiang > > > > > > At 2012-11-19 07:23:31,"Douglas Greve" <gr...@nmr.mgh.harvard.edu > <mailto: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 &nb sp; > +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 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 Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/ _______________________________________________ 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.
