[FieldTrip] fieldtrip Digest, Vol 24, Issue 16

[Lustenberger Caroline]

Dear Steve

Thank you so much for your advice. My script looks now as follows:


cfg = [];

cfg.elec = elec;

cfg.computeprob = 'yes'

cfg.neighbours = neighbours;

%cfg.latency = 'all';

cfg.frequency = 'all';

cfg.channel = 'all'%'all';%eleselection % see CHANNELSELECTION

%cfg.avgovertime = 'no';

%cfg.avgoverfreq = 'no';

cfg.avgoverchan = 'no';

cfg.statistic = 'depsamplesT';

cfg.numrandomization = 2^6;% 2^number subjects

cfg.correctm = 'cluster';

cfg.method = 'montecarlo';

cfg.clusteralpha = 0.05;

cfg.alpha = 0.05;

cfg.tail = 0;

cfg.clustertail = 0;

cfg.correcttail = 'alpha'

cfg.feedback = 'gui';

cfg.parameter = 'powspctrm';

% cfg.design = [

% 1 2 3 4 1 2 3 4 % subject number

% 1 1 1 1 2 2 2 2 ]; % condition number

cfg.design(1,:)=[1:6,1:6]

cfg.design(2,:)=[ones(1,6),ones(1,6)+1]

cfg.uvar = 1; % "subject" is unit of observation

cfg.ivar = 2;

% "condition" is the independent variable

stat = ft_freqstatistics(cfg,sd, ld);


Do you think this is now correct? We perform statistics on high-density EEG Power values and want to see whether differences that we see doing simple t-test also remain when we correct for multiple comparison.

Again many thanks and all the best
Caroline



________________________________
Von: fieldtrip-bounces at science.ru.nl [mailto:fieldtrip-bounces at science.ru.nl] Im Auftrag von Stephen Politzer-Ahles
Gesendet: Dienstag, 13. November 2012 13:59
An: fieldtrip at science.ru.nl
Betreff: Re: [FieldTrip] fieldtrip Digest, Vol 24, Issue 16

Hi Caroline,

It looks like your call is missing

cfg.correctm = 'cluster';
cfg.tail = 0;

Those are both options that I include when I do it; I'm not sure if not having those might be what's giving you the error message.

Best,
Steve

Message: 2
Date: Tue, 13 Nov 2012 08:02:22 +0000
From: Lustenberger Caroline <Caroline.Lustenberger at kispi.uzh.ch<mailto:Caroline.Lustenberger at kispi.uzh.ch>>
To: FieldTrip discussion list <fieldtrip at science.ru.nl<mailto:fieldtrip at science.ru.nl>>
Subject: Re: [FieldTrip] Cluster statistics
Message-ID:
        <7C66D90E0C18014E85B44B560D4D5BC81488F447 at EXZH1VM.kispi.int<mailto:7C66D90E0C18014E85B44B560D4D5BC81488F447 at EXZH1VM.kispi.int>>
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Dear Stephen

Thank you, It now perfectly works, but I always get this warning I'm not sure how to handle that:

Warning: doing a two-sided test without correcting p-values or alpha-level,
p-values and alpha-level will reflect one-sided tests per tail


cfg.clusteralpha = 0.05;

cfg.alpha = 0.05;

cfg.clustertail = 0;

When I want to test whether my data is significant different (direction not known, therefore two sided) with an alpha level <0.05 do I have to adjust my level to 0.025?

All the Best, Caroline
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