Questions concerning permutation tests on coherence data

Jamie Johnston johnston at KIN.UCALGARY.CA
Sat May 2 22:07:36 CEST 2009

Hi All -
I have a couple questions.  My data set consists of 10 subjects, each
performed 5 trials under 3 different conditions.  I am trying to follow
Maris et al. 2007, computing the difference between the coherence
measures (i.e. using indepsamplesZcoh)for each pair of conditions (i.e.,
3 different comparisons) and running the permutation test (montecarlo)
on this data.  My questions are:
1)      All the examples I have come across only compare two
conditions...if, as in my data, we have 3 conditions and would like to
test for differences between the three, can I simply run 3 tests
comparing all the combinations?  Is this statistically sound (sorry I am
unfamiliar with nonparametric stats).
2)      For 8 of my subjects I have 5 separate channels of data,
unfortunately for two of my subjects, I have only 4 channels (and they
are missing different channels).  I would like to include them in the
coherence averages (and statistical tests), but I'm not sure how to do
Any help would be greatly appreciated.
Jamie Johnston, Ph.D.
Assistant Professor
Faculty of Kinesiology
University of Calgary
2500 University Dr. NW
Calgary, AB
T2N 1N4
Phone: +1 (403) 220-3649
Fax: +1 (403) 284-3553
email: johnston at

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