I have 17 4-min EEG segments. I created 48 6-sec blocks per each segment and computed pwelch for each block. Then I concatenated the psd of the 48 blocks per each segment and tried to run the parametric test against baseline. This because I have 3 minutes of baseline sleep EEG before the starting of my target event and I would like to explore what happens from baseline (eg first minute) and each 6 second epoch of the event (last minute). I know it sounds more complicate than it is, so please find attached a screenshot. Any clue why am I getting this error?
I apologize, it is perhaps a very stupid question, but I am pretty new to brainstorm...
I also noticed it is saving the concatenated psd in the first block and that it is removing the first 6 seconds: why?
Concatenating multiple PSD files to create some time series is kind of a hack, we would normally use a proper time-frequency decomposition and use the option "Average by time blocks".
I understand what you did, I think it makes sense, but you have to get ready to face some weird bugs on this exotic path
The problem you have here is related with the way you define what is your baseline.
Your concatenated PSD have a time definition which might not be what you expect. Right-click on the file > File > Export to Matlab (variable "psd"), and inspect the field psd.Time.
The baseline you select in the process "Parametric test against baseline" must refer to this time vector. It must contain at least two time points (the beginning and the end of the baseline must be different), otherwise you get this error message you reported.
Note that you need many time points in the baseline in order to build evaluate correctly a mean and a standard deviation over this baseline, in order to compute a t-statistic.
