Calculating effective sigma

Dear experts,

Apologies if this is not the correct forum for my question.
I have a branch in a TTree containing the mass of a diphoton object. Is there a way to find the smallest interval which contains 68% of the events, without performing a fit (i.e not the value of the sigma parameter of the gaussian fit to the distribution)?

Thanks in advance.

On first thought, nothing comes to mind that would do this for you. A first approach could be to calculate a 68% quantile by calculating the upper and lower 16% quantiles. This is not what you want, but a first step. Now you can start to optimise the lower quantile until you get the desired quantile.

Thanks for the tip Stephan. Is there a function in ROOT to calculate the quantile? Could you point me to correct one?

Thanks again!


grep -r -i quantile `root-config --incdir`
grep -r -i quantile ${ROOTSYS}/t[eu]*

If you create a histogram of the “mass of a diphoton object”, then maybe: TH1::GetQuantiles

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