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Thank you for clarifying this confusing situation for me. I am attempting to compute Cohen's d values for regions found to be significant following Qdec group analysis using Monte Carlo simulation while controlling for multiple comparisons. I apologize for my ignorance, but is there a more accurate way to compute Cohen's d values for the regions identified using Monte Carlo simulation?
On Fri, Sep 18, 2020 at 8:03 AM Douglas Greve dgreve@mgh.harvard.edu wrote:
You have created a circularity that is classic in neuroimaging (see Vul's paper on "VooDoo Correlations"). By using only voxels inside a cluster, you have selected voxels that are sure to show hi D values
On 9/16/20 7:48 PM, Alejandro Meruelo wrote:
External Email - Use CautionHi everyone,
I reviewed some of the other answers on the mailing list to compute a Cohen's d value following the sequence of commands below for a Qdec Freesurfer analysis:
cd glmdir/contrast fscalc gamma.mgh div ../rstd.mgh -o cohensd.mgh
mri_segstats --i cohensd.mgh --seg cluster.sig.ocn.mgh --exclude 0
--sum test.output
However, my test.output file looks like:
# ColHeaders Index SegId NVoxels Volume_mm3 StructName Mean StdDev Min Max Range
1 1 2398 2398.0 Seg0001 4.9611 0.8313 3.6525 7.3172 3.6647
2 2 5893 5893.0 Seg0002 5.1281 1.1535 3.6520 8.8040 5.1520
Why are the mean Cohen's d values (4.9611, 5.1281) so large? Am I interpreting these incorrectly?
Many thanks in advance for your help, Josh
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