cluster-based permutation tests on single subjects

[Tim Curran]

Hi Eric,
Thanks for the speedy reply!  Restating my second question more simply, I am wondering how I can determine if I have enough trials in each condition.
thanks
Tim


On Jan 6, 2010, at 2:29 AM, Eric Maris wrote:

> Hi Tim,
> 
> 
> 
>> I have a few related questions about Maris and Oostenveld's (2007) method
> for
>> cluster-based permutation tests, in particular using an indepsamplesT
> statistic in a
>> between-trials design on single subjects.
>> 1. Is it problematic to have very different numbers of trials within each
> condition?
> 
> No, it is not.
> 
>> 2.  Any advice for calculating statistical power for different numbers of
> trials within
>> each condition?
> 
> I'm not sure whether I understand what you mean. Anyhow, analytical
> statistical power calculation (as is possible for T-tests and anovas) are
> not possible for permutation tests. However, one can obtain Monte Carlo
> estimates of power using simulations under the alternative hypothesis.
> 
> 
>> 3. Might it be advisable to somehow trim the trials (e.g., Leonowicz,
> Karvanen, &
>> Shishkin, 2005) to remove outliers prior to analysis?
> 
> This may increase your sensitivity. However, to obtain sound p-values, you
> must do trimming in a way that does not induce differences between the
> experimental conditions.
> 
> 
> Best,
> 
> Eric Maris
> 
> 
> 
> 
>> 
>> Any advice would be much appreciated.
>> thanks
>> Tim
>> ----------------------------------
>> The aim of this list is to facilitate the discussion between users of the
> FieldTrip
>> toolbox, to share experiences and to discuss new ideas for MEG and EEG
> analysis.
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>> http://www.ru.nl/neuroimaging/fieldtrip.
> 
> ----------------------------------
> The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/neuroimaging/fieldtrip.

----------------------------------
The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/neuroimaging/fieldtrip.