[ROOT] Errors used in TGraphErrors

From: Stilianos Kesisoglou (kesisogl@fnal.gov)
Date: Sun Aug 01 2004 - 18:25:57 MEST 

Hi,

I was wondering, which is the method implemented for the assignment of
errors in
the TGraphErrors class? The above class accepts errors on both x and y, so
how
exaclty the errors are combined for the fit? I assume there is a chi^2
function like:

             [ y-f(x) ]**2                     [ y-f(x) ]
           ------------------       or        ( -------------- ) **2
                 s**2                               s

What is the s in the above expressions? 

Thanks!

Stelios.

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