[FieldTrip] Cluster-level permutation test statistics

[Eric Maris]

Hi Valerie,

 

A dependent samples t-test (also called paired-samples t-tests) involves
pairs of observations. If you have 20 trials in one subject, 10 in
condition A and 10 in condition B, what would be your pairs (i.e., in
which natural way would you construct pairs)?

 

It may good to also read one of our papers before starting with the
tutorial. The concept of a UO is not specific to permutation-based
statistics, and given that your problem seems to be with this concept, you
could try Maris_Psychophysiology_2012, which starts out with classical
statistical tests. For cluster-based permutation statistics itself,
Maris&Oostenveld_JNM_2007 is the better choice.

 

Best, 

 

Eric Maris

 

 

From: Valerie Nunez [mailto:vnune at hunter.cuny.edu] 
Sent: donderdag 3 oktober 2013 16:23
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] Cluster-level permutation test statistics

 

Hello,

 

I'm a little confused about the notion of unit of observation (UO) as
subject or trial in the cluster_permutation_timelock tutorial:

http://fieldtrip.fcdonders.nl/tutorial/cluster_permutation_timelock

 

Specifically, I don't quite understand how the example of congruent and
incongruent trials for a single subject is considered a between-trials
design and therefore uses an independent t-test. If two trials have taken
place for one subject, why isn't this considered a within-subject design,
thereby requiring a dependent-samples t-test?

 

What am I missing?

 

Thanks,

 

Valerie

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