Tgraph&chi-square

ROOT
1

hello,
i have a TGRAPH object (not TGRAPHERROR)
i am curious how ‘root’ computes chi-square
without known errors of data points?
could you tell me that?
best regards

2

For a TGraph, all weights are equal to 1 and the chisquare is simply the sum of (y-f(fx))^2

Rene

3

ok…maybe that is not a question directly relevant with root procedure… but, what is quality of such test as compared to computing with known data points error?

p.

4

In this case the fit is OK, except that the computed chisquare has no statistical meaning. It is only the sum of the squares
of residuals.

Rene

5

:confused: ok. i understand… but is there a possibility to make statistical
sense of such a test? is there a way to define data point error having only data points and fitted points?
p.