Hi VM, Please see below:
On 1 February 2017 at 02:38, neuroimage analyst < neuroimage.anal...@gmail.com> wrote: > Hi, > > We extracted volume measures from 7 ROIs in 2 groups and compared > a) Mean of each ROI volume between group, and compared independently such > as > i) whether mean of ROI 1 in group 1 is equal to mean of ROI1 in group 2 > ii)whether mean of ROI 2 in group 1 is equal to mean of ROI2 in group 2 > and so on > This means 7 comparisons, or 14 if you test both directions (tails) separately. > > b) Plotted the mean ROI volume for 2 independent measures and compared > whether the slope between and within group is significantly different. such > as > i) Slope of ROI1 is positively associated with MoCA , age (grp1) ? > ii) Slope of ROI1 is negatively associated with MoCA, age (grp2) ? > iii) Slope of ROI1 vs MoCA (grp1) is significantly different than slope of > ROI1 vs MoCA (grp2) ? > iv) Slope of ROI1 vs MoCA (grp2) is significantly different than slope of > ROI2 vs MoCA (grp2) ? > These sound tests for main effects and interaction, with various combinations possible. > > Q1) Do we have to perform multiple comparisons for (a) and (b)? > Yes. > Q2) If yes, do we correct across 7 measurements for (a) and 2 measurements > for (b) or 7 measurements for both (a) and (b)? > You could put the values for the 7 ROIs in a table in .csv format, with one column per ROI and one row per subject. This would be the input data. Create a design matrix as: EV1: 0 or 1 coding for group 1 EV2: 0 or 1 coding for group 2 EV3: MoCA group 1 EV4: MoCA group 2 EV5: Age group 1 EV6: Age group 2 etc Then define a set of contrasts such as: C1: [1 -1 0 0 0 0 ...] - This tests if mean for group 1 > mean for group 2 C2: [-1 1 0 0 0 0 ...] - This tests if mean for group 1 < mean for group 2 C3: [0 0 1 -1 0 0 ...] - This tests if the slope for MoCA for group 1 > slope for MoCA for group 2 C4: [0 0 -1 1 0 0 ...] - This tests if the slope for MoCA for group 1 < slope for MoCA for group 2 C5: [0 0 1 0 0 0 ...] - This tests if slope for MoCA for group 1 > 0 C6: [0 0 -1 0 0 0 ...] - This tests if slope for MoCA for group 1 < 0 etc You'd run this analysis in PALM with something as: *palm -i input.csv -d design.mat -t design.con -corrcon -o myresults -logp* Hope this helps! All the best, Anderson > There is evidence to both performing and nonperforming multiple > comparisons In the literature. > > Any response (hopefully pointing to a literature) will be greatly > appreciated. > > Thanks > > Regards > > --VM > > _______________________________________________ > 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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