[FieldTrip] Post hoc comparison following cluster-based permutation test

Blume Christine christine.blume at sbg.ac.at
Tue Aug 15 13:15:37 CEST 2017

Hi Tom,

Thanks a lot indeed for the quick reply. I do find significant differences between A_avg and B_avg in the frequency range where I expect them following the results from the within condition comparisons. Although it is not directly comparable because clusters may obviously differ, I guess that is the best I can do.

Thanks again!


Von: fieldtrip-bounces at science.ru.nl [mailto:fieldtrip-bounces at science.ru.nl] Im Auftrag von Marshall, T.R. (Tom)
Gesendet: Montag, 14. August 2017 10:10
An: FieldTrip discussion list
Betreff: Re: [FieldTrip] Post hoc comparison following cluster-based permutation test

Hi Christine,

If I understand correctly:

    For each subject you have four conditions - A_face, A_house, B_face, B_house
    You compared A_face with A_house and there was a significant difference
    You compared B_face with B_house and there was also a significant difference


Now the reviewers want you to test if there is a difference between A and B

You could:

    For every subject, create an average of A_face and A_house (let's call it A_avg)
    For every subject, create an average of B_face and B_house (let's call it B_avg)
    Compare A_avg and B_avg using depsamplesT

From: fieldtrip-bounces at science.ru.nl<mailto:fieldtrip-bounces at science.ru.nl> [fieldtrip-bounces at science.ru.nl] on behalf of Blume Christine [christine.blume at sbg.ac.at]
Sent: 14 August 2017 08:40
To: FieldTrip discussion list (fieldtrip at science.ru.nl<mailto:fieldtrip at science.ru.nl>)
Subject: [FieldTrip] Post hoc comparison following cluster-based permutation test
Dear all,

I am comparing event-related oscillatory responses in two conditions A and B. In each condition, subjects have been presented with two different stimulus types, let's take "houses" and "faces" as an easy example. What I have done so far is I compared the oscillatory responses to the two stimuli WITHIN each condition using cluster based permutation tests (depsamplesT; frequency range 4-15 Hz, 173 electrodes, 6 time bins). What I find is significant differences between "houses" and "faces" within each condition. However it seems that in higher frequencies there is also a difference between conditions A and B. Now reviewers have asked me to test this difference statistically. Unfortunately, I do not really know how to go about...any suggestions are highly appreciated!


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