[FieldTrip] ft_freqstatistics for between subject design
"Jörn M. Horschig"
jm.horschig at donders.ru.nl
Wed Mar 19 15:28:04 CET 2014
Hi BeomJun Min,
> I think that each 5 values correspond with the frequency data point.
yes, that;s correct.
>
> Is that script suitable for the test for the significance, especially
> avgovertime option 'yes'?
Yes and no. Yes, because you are testing for significance and, depending
on what hypothesis you have, averaging over time is perfectly fine. Use
avgovertime if you are looking for an effect independent of time,
otherwise set it to 'no'. No, because you should pay attention to why
selecting this time-frequency region. Now it seems that you selected
frequency and time window based on eyeballing the data. If you have no
apriori hypothesis about these frequencies and time window, it's a
faulty approach to just select the region that shows the strongest
approach and do a statistical test. You should take the whole
time-window and whole freuqency spectrum (narrowed down as much as
apriori hypotheses allow). If this is a real effect it is likely that a
proper statistical test will show up only around that time-frequency.
>
> If I change the avgovertime option to 'no', then can I found the
> p-values for each frequencies(5 values), and each time point(51
> values), in total 255 values that could have multiple comparison issue?
Yes, you have this problem, is there a reason why you are not using the
cluster-based permutation test (or any other correction for multiple
comparison which is implemented by setting the cfg.correctm parameter
accordingly)?
>
> And I thought the 'mask' values of 0 indicates 'statistically
> non-significance'. Is that right?
Yes, that is correct.
Best,
Jörn
>
> --
> BeomJun Min, M.D.
>
> Department of Medical System Engineering (DMSE)
> Gwangju Institute of Science and Technology (GIST)
> 261 Cheomdan-gwagiro(Oryong-dong), Buk-gu, Gwangju
> 500-712, Republic of Korea (South)
> Phone: +82-62-715-3266 / Fax: +82-62-715-3244
> E-mail: mbj0310 at gmail.com <mailto:mbj0310 at gmail.com>,
> http://bmssa.gist.ac.kr <http://bmssa.gist.ac.kr/>
>
>
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--
Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen
Neuronal Oscillations Group
FieldTrip Development Team
P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands
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