help > RE: Is small cluster size problematic?
Jul 11, 2018  04:07 AM | Alfonso Nieto-Castanon - McGovern Institute for Brain Research. MIT
RE: Is small cluster size problematic?

That is strange, could you please give me more details about how you have specified&run your second-level model? This may have been caused by a problem in the estimation of the smoothing level of the residuals and/or in the assumptions of the RFT model used for cluster-level statistics, so perhaps a good idea would be to select the 'non-parametric stats' option in CONN's results explorer window in order to have CONN run permutation/randomization tests for cluster-level stats instead.

Hope this helps
Originally posted by wzhong:

I have run some second-level seed-to-voxel analysis in conn. My model is quite simple: I am using multiple regression to find the voxels whose connectivity with a few ROI seed regions correlate with a behavioral variable of interest after covarying out mean FD, age and gender. I use a height extent of p<0.001 uncorrected and a cluster correction of p<0.05 FDR. I have a few significant results for multiple seed regions, but the size of the significant clusters are very small; the largest is about 50 voxels and many are between 15 and 30 voxels in size. I am wondering whether this would be problematic and if so what may have caused the problem.


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wzhong Jul 6, 2018
RE: Is small cluster size problematic?
Alfonso Nieto-Castanon Jul 11, 2018
wzhong Jul 11, 2018
Alfonso Nieto-Castanon Jul 12, 2018