How to calculate error in ROOT

[Wile_E_Coyote]

Questions about getting events in each bin/checking error bar is correct or not

Hi, How are you confident that the error is too large or too small ? Do you know the probability distribution of the observed bin content ? What the bin content represents for you ? If the bin content represent counts, and the histogram normalisation is not fixed, the distribution is a Poisson and the estimated error in ROOT is the one assuming the true value of the Poisson is the observed bin count. If you are filling the histogram with weighted counts, then an approximated procedure is us…