[FieldTrip] permutation test: multiple comparison correction for the p-values

[Julian Keil]

Hi Iris,

I'm not sure what you want to do with the p-values in the following, but you can multiply your (FDR-corrected) mask with the prob.
This would look like this: stat_TF.prob_new = stat_TF.prob .* stat_TF.mask;

Now you only have the significant p-values left in your prob_new-field, everything else is set to 0.

Hope this helps

Julian

********************
Dr. Julian Keil

AG Multisensorische Integration
Psychiatrische Universitätsklinik
der Charité im St. Hedwig-Krankenhaus
Große Hamburger Straße 5-11, Raum A007
10115 Berlin

Telefon: +49-30-2311-1879
Fax:        +49-30-2311-2209
http://psy-ccm.charite.de/forschung/bildgebung/ag_multisensorische_integration

Am 13.11.2015 um 09:41 schrieb Steinmann, Iris:

> Hi everybody,
> 
> I' m using the 'ft_freqstatistics' function to find significant differences between two time-frequency spectra
> (see the used options down below).
> While fieldtrip calculates the permutation test it throws the following information:
> 
> "performing FDR correction for multiple comparisons
> the returned probabilities are uncorrected, the thresholded mask is corrected"
> 
> Since I'm using the p-values for the following analysis and not the thresholded mask, I was wondering how I
> get my p-values corrected for multiple comparison?
> 
> Does anyone has an idea? Thanks in advance!
> 
> 
> I used the following options:
> 
> cfg = [];
> cfg.channel     = 'all';
> cfg.latency     = [2.3 2.8];
> cfg.avgoverchan = 'yes';
> cfg.avgovertime = 'no';
> cfg.frequency = [9 14];
> cfg.parameter   = 'powspctrm';
> cfg.alpha = 0.05;
> cfg.tail = 0;
> cfg.correctm = 'fdr';
> cfg.correcttail = 'prob';
> cfg.ivar = 1;
> cfg.statistic = 'ft_statfun_indepsamplesT';
> cfg.method = 'montecarlo';
> cfg.design = design; % defined in at the beginning of the function
> cfg.numrandomization = 1000;
> 
> stat_TF = ft_freqstatistics(cfg, TF_remove, TF_noremove)
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> fieldtrip at donders.ru.nl
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