[G12] Moment errors

[Carlos Salgado]

Dear Paul

Thanks for your note!
I do not know if i can follow your math...but I agree in your final answer.

And ROOT will handle the errors just fine, if you plot the mass bins weighted by the H(LM)
(see https://savannah.cern.ch/bugs/?19497)

if the weights w_i = H_i (unnormalizaed moment)

the error in the bin (weigthed)  mean is = RMS/sqrt(N_eff)
where N_eff=(sum_w_i)^2/sum_(w_i)^2

therefore  error_in_mean = RMS/(sum_w_i) x sqrt(sum_(w_i)^2)

if we assume Poisson distributions RMS = (sum_w_i) (mean)

therefore error= sqrt(sum_(w_i)^2) = sqrt(sum_(H_i)^2) since w_i=H_i
same as your result.

and that is what ROOT does as far as I can tell.

See you. Carlos

----- Original Message -----
From: eugenio at fsu.edu
To: "g12" <g12 at jlab.org>
Sent: Tuesday, August 21, 2012 3:47:29 PM
Subject: [G12] Moment errors

Folks,

Attached is a note regarding the error calculation for unnormalized moments.



Paul





--
Prof. Paul Eugenio
Florida State University
Department of Physics
Tallahassee, Florida,  USA 32306

(850) 325-0314
eugenio at fsu.edu





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