Hi Francois,
The baseline correction using z transformation is not changing the baseline epoch (-100 to 0 ms) but if I run this command twice (standardize>z transformation), the baseline gets corrected. Is it scientifically correct to run it twice?What may be the reason for this?
I'm sorry, I don't exactly understand your question.
When running the process "Standardize > Baseline normalization", it does affect all the time points in the epoch, no matter which option you select (Z-score or other).
Please post screen captures illustrating what you are trying to do and showing what you think is not working correctly.