Troubles with AsymptoticCalculator

[Luca_Maria_De_Vita]

Hi Experts,
this is my first topic and actually these days are the first ones using PyROOT after a course about it and this is a kind of homework.
My aim is to do an hypothesis test with asymptotic calculator. I have a dataset, a workspace with two models: one with bkg only (null) and one with bkg+sgn (alternate) pdf. Actually they have the same PDF, but for my poi I setted a snapshot with zero value, namely no signal. Then I pass everything to my constructor:

ac = ROOT.RooStats.AsymptoticCalculator(dataset, nullModel, altModel)

When I use NullPValue() I obtain a p-value of exactly 0.5, but this has no meaning in my opinion. The null hyp. correspondes to have no peak for psi(2S) (the second, little peak in the attached image). How can I solve this? Maybe something is wrong in settings of snapshots for the two hypothesis or something different in the constructor?
Thanks a lot for help

[lbreitwi]

Hi @Luca_Maria_De_Vita

Welcome to the community! Glad to read that you are learning about ROOT.
From your posting it seems that there is no ROOT specific issue.
I am convinced that you will learn the most if you solve your homework question by yourself.

However, if you do find a problem, bug, or have a suggestion for improvement, please do come back and let us know.

All the best,
Lukas

PS: Here some tips for efficient and successful posting