[FieldTrip] Nonparametric statistical testing of phase coherence

Ana Navarro Cebrian sabato45 at hotmail.com
Tue Apr 9 19:57:23 CEST 2013

Hi Maris,thank you for your response.I think my question wasn't clear. Let me rephrase it. I'd like to apply the montecarlo approach that you explain in Maris et al., because I havetwo conditions (errors vs correct responses) with a huge difference in the number of trials. In this case, I understand that I have to apply the montercarlo simulationacross trials to find out whether condition 1 is different from condition 2 independently of their different number of trials.If that's correct, my question is, do I get a p-value from this procedure? If so, after performing the same analysis for each subject independently, I'll end up with a p-value for each subject. Is that correct?
I'm sorry if I'm not understanding something basic.I really appreciate your help.Ana 


From: e.maris at psych.ru.nl
To: fieldtrip at science.ru.nl
Date: Tue, 9 Apr 2013 12:09:03 +0200
Subject: Re: [FieldTrip] Nonparametric statistical testing of phase coherence

Hi Ana, To compare coherence between conditions across subjects (instead of trials), you need a different statfun: depsamplesT (for a within-subjects design; subjects have participated in all conditions) or indepsamplesT  (for a between-subjects design; subjects have participated in only one condition). Typically, this type of test is performed using power as the dependent variable, but exactly the same test is used for comparing coherence in a multiple-subject study. However, you will have to specify the cfg.parameter field when calling ft_freqstatistics such that it points to the data field that contains your coherence data (importantly, for a given reference channel). Good luck, Eric Maris  From: Ana Navarro Cebrian [mailto:sabato45 at hotmail.com] 
Sent: vrijdag 5 april 2013 23:56
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] Nonparametric statistical testing of phase coherence 
Hello everybody,I'd like to use the test proposed in Maris et al., 2007 (that I believe is implemented in statistics_montecarlo.m?). I'm calculating the difference in phase coherence between two conditions. The problem is that one condition has much less trials than the other, so I imagine the Montecarlo simulation would need to be across trials, in which case, I'd end up with a p-value for each individual subject, right? I'm not sure then how to apply this across subjects. The Maris et al. paper is very clear, but it only explains single subject analysis. I hope that makes any sense. I appreciate any help.Thanks,Ana  
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