[Ifeffit] error

[JeongEunSuk]

Hi all
I fitted ZnMgO to know whether Mg is sited on Zn position.
the method of fitting as following;
1st :  to fit with some Mg located on Zn site.
2nd:  to fit with some Mg which position is different from Zn cite
The parameters for Mg like bonding length, disorder and others were set.
When I was fitting, there are only 8 parameters in both two method. So that independent data point and variables are same.
 
Both 1st and 2nd had same R-factor but reduced chi-square of 1st was lager than that of 2nd.
It has been known that R-factor is independent of error( uncertainty in the measurement) but reduced
chi-squrare is inverse proportional to error^2. 
So I think that same R-factor and different reduced chi-square  for two method mean the fittings of two method are not different, 
but  error used in reduced chi-square is different.
I want to know how the error used in reduced chi-square is decided in FEFFIT code. 
  		 	   		  
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