deletions | additions       diff --git a/Statistical analysis.tex b/Statistical analysis.tex  index 0b786b6..327598e 100644  --- a/Statistical analysis.tex  +++ b/Statistical analysis.tex 
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\end{equation}  This analytical procedure is used in Ref.~\cite{Grzadkowski_2000} to determine the sensitivity to top-quark electroweak couplings in $500\,{\rm fb}^{-1}$ of ${\rm e^+ e^-}$ collisions at $\sqrt{s} = 500$\,GeV, with or without incoming beam polarization. In this article, the authors evaluate the covariance matrix with Eq.~\ref{eq:rate}, but they let the total number of events float by adding a fictitious multiplicative form factor $\delta_0$ in front of $S^0$ in Eq.~\ref{eq:optimal}, hence increase the rank of the covariance matrix from 8 to 9. It was checked that this work-around is numerically equivalent to using Eq.~\ref{eq:norate}, {\it i.e.}, to not use the total event rate in the likelihood.   A quick survey of Fig.~\ref{fig:distributions}, however, shows that $f_A^\gamma(x,\cos\theta)$, in the top-left corner, is almost degenerate with the standard model contribution $S^0(x,\cos\theta)$, in the bottom-right corner. Letting the normalization of the standard model contribution float is therefore bound to lead to very large statistical uncertainties on all form factors, as is indeed observed in Ref.~\cite{Grzadkowski_2000}. For this reason, and as is done in Ref.~\cite{Baer_2013}, the present study includes the total event rate in the determination of the uncertainties, leading to an improvement by factors up to 50 with respect to not using it. uncertainties.  As already mentioned, it is possible to determine simultaneously all eight form factors and their uncertainties. In the first configuration of Ref.~\cite{Baer_2013}, however, only the three coefficients $F_{1V}^\gamma$, $F_{1V}^Z$ and $F_{1A}^Z$ are allowed to vary. The other five form factors are fixed to their standard model values. In this simplified situation, Eq.~\ref{eq:optimal} reads  \begin{equation}