Sigma for an observable

1. Mar 30, 2015

Safinaz

Hi all,

I'd like to understand what does it mean by allowed 1 or 2 $\sigma$ regions for some observable, like R(D) in Fig. 1 left [ 1206.2634v2] ?

And how can I calculate or plot this value or region according to any theoritical model ..

Bests.

2. Mar 30, 2015

Orodruin

Staff Emeritus
Standard deviations have to do with experimental precision. It is not something you derive from the theoretical model.

If a parameter set is within the $1\sigma$ region, it means that if reality is described by the theory and with those particular parameter values, then the result is within the 68% least extreme outcomes you could have found in the experiment. For all parameter sets outside of the allowed $1\sigma$ region, the results are among the 32% most extreme results given those parameters and the parameter set is rejected at $1\sigma$ (or "at the 68% confidence level").

Footnote: This naturally requires you to define what you mean by an outcome being extreme.