[Eeglablist] Unequal group size and STUDY use

[Michael Stevens]

Hi everyone,

Sorry if this is a known issue that I just didn't see in previous posts... But it'd be quite helpful if someone could confirm a problem/limitation.  I had been beating my head against my computer trying to figure out why I couldn't get simple group stats to display properly when doing t-tests (and similar analyses) in a STUDY.  I first thought it was code I whipped up to create the STUDY, then I thought I had a bad dataset somehow in the mix, etc.  However, one of my students and I were working on this when she finally noticed that group comparison results could be visualized perfectly when there were equal numbers of participants in each group.  Until that time, I had been trying to compare one group of 26 subjects with another of 19.  Sure enough, when I selected exactly 19 vs 19, all the results/visualization plots worked fine.  Until then for instance, it'd give me ERP plots for one group, but blank plots for the second, etc.

Is this a known issue?  Or perhaps it was just something I was doing wrong locally?  Obviously, it'd be more flexible to be able to use unequal numbers of participants in group comparisons.  

Thanks for anyone who can confirm this, or just point to something I'm doing wrong.  (FYI - I'm using the version of EEGLAB as of 10/08, the most recent one as far as I know - 6.03b, I think).

Best,
Mike


Michael C. Stevens, Ph.D.

Director, Child and Adolescent Research
The Institute of Living / Hartford Hospital

Director, Clinical Neuroscience & Development Laboratory
Olin Neuropsychiatry Research Center

Assistant Clinical Professor of Psychiatry
Yale University School of Medicine

Contact Information:
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ONRC, Whitehall Building
Hartford, CT  06106

Tel: (860) 545-7552
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