[Eeglablist] Fwd: 4 questions about Study statistics

[Cyril Pernet]

Hi there,

we just published a new toolbox (LIMO EEG) which allows to this kind of 
analysis no problem - indeed it deals with any designs :-)
you will have to analyze each subject (1st level) specifying the 2 
conditions which will allow you to obtain beta parameters (or regression 
coef if you prefer) for each condition (and electrodes and time frames). 
Then perform a second level analysis you can do the repeated measure x 
gp anova on those beta parameters (see hierarchical linear model in 
wikipedia). At this stage our toolbox uses bootstrap and 
spatial-temporal clustering to correct for multiple comparisons. Such 
analysis will tell you if, at the population level, you have gp 
differences, conditions differences and interactions (again for all 
electrodes and time frames if you wish).

You can find the toolbox here 
https://gforge.dcn.ed.ac.uk/gf/project/limo_eeg/
and paper here http://www.hindawi.com/journals/cin/2011/831409/

Best
Cyril

>
>>> 2) Non-bootstrap options:  for permutation or parametric, and 
>>> calculating stats on first and second variable, the matlab window 
>>> output suggests that I should not be running this type of ANOVA on 
>>> the parametric/permutation data, e.g.:
>>>
>>> ... (2 balanced 1-way ANOVAS and then 4 paired t-tests)
>>> 4 x 2, unpaired data, computing F values
>>> Using balanced 2-way ANOVA*/(not suitable for parametric testing, 
>>> only bootstrap)/*
>>> ...
>>
>>
>> You have a mixed design (paired for one variable and unpaired for the 
>> other one). Therefore the balanced Anova is not strictly correct 
>> (both variables should be unpaired). For permutation, it does not 
>> really matter (the ANOVA computation is just a way to compute a 
>> combined 2x2 measure - and the pairing of values is preserved based 
>> on your settings during the permutation). There is no functions in 
>> Matlab to handle this special case to our knowledge, but there is one 
>> in "R". Email David Groppe for more info <dgroppe at cogsci.ucsd.edu 
>> <mailto:dgroppe at cogsci.ucsd.edu>>.
>>
>>
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>


-- 
Dr Cyril Pernet,
Academic Fellow
SBIRC fMRI Manager

SFC Brain Imaging Research Center
Division of Clinical Neurosciences
University of Edinburgh
Western General Hospital
Crewe Road
Edinburgh
EH4 2XU
Scotland, UK

cyril.pernet at ed.ac.uk
tel: +44(0)1315373661
http://www.sbirc.ed.ac.uk/cyril
http://www.sinapse.ac.uk/

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