Using Roofit, I tried to fit a binned distribution (with thousands of events), with chi2 as well as likelihood fit,
why they give quite different answers (about 3% change) ?
(1) With unbinned fit to same distribution, I got parameter value 1.478
(2) With 100 bins, likelihood fit i also got 1.478
(3) as i decrease the bin# to 10bins…the parameter value increases to 1.51.
(4) However with same 10 bins, the chi2 fit gives me 1.478…
Can you suggest whats going on ?