 |
 |
PS: If you choose to use PALM, with the 4 timepoints, consider using the "-ise" option. It doesn't require compound symmetry, but requires that the errors themselves are symmetrical (i.e., have a symmetrical distribution around zero). On 30 May 2017 at 23:23, Anderson M. Winkler <[log in to unmask]> wrote: > Hi Kavous, > > What are the research hypotheses? If it's about changes over timepoints, > and interaction group by timepoint, then this needs the assumption of > compound symmetry, which is fine for 2 timepoints, but becomes harder with > 4. If you want to make that assumption, then you can use PALM, defining one > exchangeablity block per subject, and permuting within-block and also > whole-block (for the interactions. > > If you can't make the compound symmetry assumption, consider Bryan > Guillaume's toolbox called SwE. It seems the most recent version is on > GitHub: https://github.com/BryanGuillaume/SwE-toolbox > > If, however, the hypothesis is about group differences regardless of > changes in time, then randomise can be used directly, with the option > --permuteBlocks. This is the Example 6 of the randomise paper: > http://www.sciencedirect.com/science/article/pii/S1053811914000913 > > Hope this helps! > > All the best, > > Anderson > > > On 30 May 2017 at 05:05, Kavous <[log in to unmask]> wrote: > >> Hi FSLers, >> >> I'm going to analyze a longitudinal VBM between 3 groups and within 4 >> time-points. >> >> By reading following discussions, I know that in 2 time-points analysis I >> have to use all my subjects' data to make a study-specific template and >> subtract pre-post data after smoothing for randomise analysis. >> >> https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=FSL;d6651f48.1008 >> https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=FSL;3dc8868b.1408 >> >> However, my question is that is there any way to consider all 4 >> time-points in a single analysis? >> >> Thanks, >> Kavous >> > >