Transformations towards the normal distribution of broad band spectral parameters of the EEG

In this report transformations are evaluated for obtaining normally distributed broad band spectral parameters (both for absolute and relative power) in a sample of healthy individuals. This problem leads automatically to the question of defining a normative sample, both in terms of sampling and recording conditions; as to the latter, the electro-oculogram proved to be crucial. For relative power the transformation log(x/(1-x)) was excellent in all regards, whereas the best transformation for absolute power--log(x)--was not fully satisfactory for all bands.