[Eeglablist] Unequal group size and STUDY use

[Hamish INNES-BROWN]

Hi Micheal, yep, the same thing happens with my data.

I can get ERSP and ITC statistics with unequal groups, but not ERP
stats.

At the moment I plan to work out how run the stats myself, either using
the EEGLAB data structure or by exporting, but I haven't started that.

I too would be glad of any pointers antone can give! 


Hamish Innes-Brown
Senior Research Assistant

The Bionic Ear Institute
c/o St Vincents Hospital
6th Floor Daly Wing,
35 Victoria Pde, Fitzroy Vic 3065
Tel: +61 3 9288 3523
Fax: +61 3 6997 7518

-----Original Message-----
From: eeglablist-bounces at sccn.ucsd.edu
[mailto:eeglablist-bounces at sccn.ucsd.edu] On Behalf Of Michael Stevens
Sent: Tuesday, 25 November 2008 4:38 AM
To: eeglablist at sccn.ucsd.edu
Subject: [Eeglablist] Unequal group size and STUDY use

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:
200 Retreat Avenue
ONRC, Whitehall Building
Hartford, CT  06106

Tel: (860) 545-7552
Fax: (860) 545-7797


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