[Eeglablist] Grand Average

[Alberto Gonzalez V]

Hi to all,

I have a question about ERP methodology. Consider that we record the EEG during and task  in 3 subjects, then we do the averages  ( considering that the task has 60 epochs):
	Subject 1  did a perfect task, so we did the average with 60 epochs.
	Subject 2 had some problems during the recording, and the average was done with 40 epochs.
	Subject 3 had only 20 epochs, but we think that it´s enough and did the average.

So the Subj 1 has all the epochs =1, Subj 2 has = 2/3 of the epochs, and Subj 3 has only =1/3. But in the grand averages we treat them as they had all the epochs (=1). Isn't better to give each subject a proportional value (considering it's number of epochs) in the grand average(something like:  ([Subj1*1]+[Subj2*2/3]+[Subj3*1/3])/2)?.

Thanks for your time!!!