Hi Gong,
I looked at your histogram. You have a few points for which the errors
do not seem correct. I do not know how you filled your histogram.
If you add the 3 following lines
etac->SetBinError(18,20);
etac->SetBinError(23,20);
etac->SetBinError(43,20);
to set bigger error bars for these 3 bins and fit with the simple
loglikelihood method
his->Fit(FunName,"L0");
then you will get a chi2/ndf = 190/189
Rene Brun
On
Wed, 26 Feb 2003, Datao Gong wrote:
> Hi,Rooters,
> I fit my ntuple with likelihood method. I found if i tightly cut,
> the fit result is much different and fit quality worse (ch2/ndf far
> away from 1). Compare to min_fit, i found it is from the empty bins
> in histogram. Likelihood method seems do not take into account
> empty bin default. (I read Burn's email in roottalk02). In my case,
> I fit my histogram with option "EMVL0", the ch2/ndf is 237/189, meanwhile,
> mn_fit give me 190/191. I know there are two empty bins in my histogram.
> If i set "W" option, the chi2/ndf is up to 3067/191. Is there something
> wrong?
>
> Gong Datao
>
>
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