I’m trying to do a two-component fit to a mixed distribution. All spectra are generated by functions. The component spectra is generated from the exponential function ( bkg = exp[ -|b|(x+1) ] and sig = exp[ |s|(x-1) ] ), while the mixed spectrum is generated by the weighted sum of those functions.

An example of the spectra and the fit is in [1]

The error obtained from TFractionFitter::GetResult( component, result, error) always show larger value than result. ( for example, result = 0.2 and error = 0.3 ).
I found these values strange because I have quite large statistic ( >1000 events in each spectrum).
I would like to ask if treat the error as absolute error is correct, or should I treat it as the relative error of the result?

Thank you,
Hoa

[1] A fit plot
Blue: background, yellow: signal, black-dot: mixed sample.

Hi,
The error you are getting the fraction from TFractionFitter is the absolute error on the fractions.It is strange you set such large errors, something strange is happening.
Can you please post your example code, so I can reproduce the problem ?