Hi Antonio,
a few questions:
1) What is the difference between Thorsten's signal function you have
used in your fits documented at April 4th compared with what is
used now?
In that configuration the fit worked reasonably well also on data
and since we are behind the time schedule I would vote to use this
configuration.
2) Concerning the chi^2 scaling:
a) I'm not sure if I really understood how the errors on the fit
parameters have been calculated. Did you do it by yourself?
Could you please be more specific?
b) A chi^2 fit can be screwed up if there are bins with very small
statistics or even zero entries.
Is the range in the histogram constrained?
Cheers,
Heiko
On Fri, 21 Apr 2006, Antonio Petrella wrote:
>
>
> Hi Kerstin,
>
> > since numbers are so different I am still wondering whether I compare
> > the correct tables... Is the table from today and the table from April
> > 12 (not using any links but the tables directly on the main page) the
> > correct ones to compare?
>
> Yes that's correct. I would have expected that the yields for the All MC
> fit from April 12 (NLL fit) and the yields for the fit with no error
> scaling from April 20 (Chi^2 fit) were the same.
>
> > If so, the yields are so different that it should be enough to just
> > compare them to the number of events in the histograms to tell us
> > which fit obviously gives us weird numbers... have you looked at that?
> >
>
> Yes, since the dataset is the same for both fits, and has 1561024
> entries, the wrong one is certainly the minimum chi^2 fit.
>
>
> Antonio
> > Cheers,
> > Kerstin
> >
> >
> > On Thu, 20 Apr 2006, Antonio Petrella wrote:
> >
> >> Hi Kerstin,
> >> that is exactly what I meant. The sample is right the same but yields
> >> are different. This happened just by switching to chi^2 fit.
> >>
> >> Probably I'm doing something wrong... but it's not clear to me where: I
> >> have followed the example on roofit web site
> >> (http://roofit.sourceforge.net/docs/classref/examples/fitgen3.cc.html)
> >> to make the chi^2 fit.
> >>
> >> Do ou have any suggestion?
> >>
> >> Bye...
> >> Antonio
> >>
> >> Kerstin Tackmann ha scritto:
> >>> Hi Antonio,
> >>>
> >>> can you be a little more clear what you mean by "numbers look quite
> >>> strange"? Do you fit the same samples as on April 12th? The yields
> >>> seem to be very different. But maybe I am just not comparing the
> >>> correct numbers...
> >>>
> >>> Thanks,
> >>> Kerstin
> >>>
> >>> On Thu, 20 Apr 2006, Antonio Petrella wrote:
> >>>
> >>>> Hi all,
> >>>>
> >>>> on the web page
> >>>> http://www.slac.stanford.edu/~petrella/mesfits/mesfits.html
> >>>>
> >>>> I posted the result of the chi^2 scaling using a minimum chi^2 fit.
> >>>> This time we can see a variation on the yields and errors, but numbers
> >>>> look quite strange...
> >>>>
> >>>> Antonio
> >>>>
> >>>>
>
