Random Averaging

Abstract

The idea of this tutorial is to provide a procedure for random averaging of row data containing triggers. The advantage of random averaging is that the result is not only one average over the trials but many different averages of the same data with different choice of trials and these averages can be statistically analyzed in order to get a statistically verified differences between the signal before and the signal after the trigger point. This can be applied e.g. in the source space and it can be used to determine brain regions with a statistically significant activity against baseline. All steps in this article are demonstrated on a file from the examples of BESA Research - "S1.cnt".

Export the single trial data in simple binary file format

Load from the examples of BESA Research the file "S1.cnt" in the folder "ERP-Auditory-Intensity". After the file was loaded select menu "File -> Export...". The "Export data" dialog opens (see Figure 1). In that dialog select "Epochs around triggers" in the section "Data to export". The two buttons "Interval..." and "Triggers..." become active. Then click on "Interval..." to set appropriate values for the time interval around the trigger and after that click on "Triggers..." in order to select trigger for the random averaging. Please make sure to select only one trigger (see Figure 2) else the generated random averages will contain mixed data from all selected triggers. In the "Export data"-dialog click "OK" to export the data.