[FieldTrip] 3x2 ANOVA using permutation tests?

[Snijders, T.M. (Tineke)]

Hi Anne,

To first do the analysis on separate groups, and then do an ANOVA on the resulting time-windows comparing the groups is double dipping.

The simplest solution is to first do the cluster randomization test on all 3 groups together (i.e. treat them as 1 group), and compare the 2 conditions (so just a depsamplesT).
Based on this you get a time-window & electrodes that show a difference between conditions.
You then extract the subject means from this time-window&electrodes (meaning you get one value per subject per condition), and use these in an ANOVA to compare the different groups, and to look at the effect of the behavioral regressor.

Alternatively, you can use the difference scores (condition 2- condition 1) as an input for the cluster randomization, with the three groups as between-subject factor (indepsamplesF).

Best,

Tineke



________________________________
From: fieldtrip-bounces at science.ru.nl [fieldtrip-bounces at science.ru.nl] on behalf of Anne Mickan [amickan1990 at gmail.com]
Sent: Monday, July 18, 2016 2:22 PM
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] 3x2 ANOVA using permutation tests?

Dear fieldtrip community,

I've been using cluster-based permutation tests to analysis my EEG data in which I have 3 groups and 2 conditions each. Ultimately I want to know whether groups differ from each other with respect to differences in conditions. In a traditional analysis I would do an ANOVA on preselected time-windows, but I haven't been able to figure out how to properly do that within the permutation test.

So far I simply did permutation tests for each of the groups separately. Then on the basis of these I choose windows for an ANOVA (and a regression analysis with some behavioral measures I acquired). Is that OK? Or is there a way to do the permutation tests for all groups together and add group as a between-subject factor (in addition to the within-subjects factor condition)? And would that be better / obligatory to do (instead of what I did so far).

How do I need to change the cfg.design in order to do that?

Thanks a lot in advance!

Best,
Anne
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