[Eeglablist] singletrials option in std_erpplot

[Hamish INNES-BROWN]

Hi all, I feel like this is a bit of a stupid question, but I'm having trouble working out what the 'use single trials where available' option does in the std_erpplot function (when plotting channel ERPs).

When pre-computing the channel measures I have enabled the 'save single trial measures' for the ERP only (not for the ERSP or ITC), and for the moment I'm only looking at the channel ERPs.

I have a simple STUDY, with 12 subjects and 2 conditions. At the moment I'm not using the STUDY.design, rather I have made up a study with all separate data files for each condition, but I don't think this should matter.

The question is, what is the difference between the statistics calculated for each electrode (whether it's parametric or permutation), when the 'use single trial data' option is switched either on or off.  There is obviously a difference, and the matlab output switches from one-tailed to 2-tailed if you use the parametric option, but I'm not clear on what's being done.

If Ns = number of subjects and ntrials = number of trials, and the 'use trial info' button is switched on, is the condition difference calculated for every trial and every subject, collapsing all the subjects into one huge pool of trials and using Ns*ntrials as the final N value?

And if not, I guess the mean of all the trials or each subject is used (in the usual way), and the N is the number of subjects?





Hamish Innes-Brown
Music & Pitch Project
Bionic Ear Institute
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