Hi @Dil ,
if I understand correctly, this is less a question about ROOT and more a question about statistics. Let’s see if @moneta has some suggestions, otherwise you should ask your research group’s statistics expert.

Hi,
The total error (statistical one and the one given by the weights uncertainties) can be approximated with sqrt{err_weight(bin i)^2 + err_syst(bin i)^2} using your definitions or err_weight and err_syst.