  The error probability of the discrimination of the Standard Model (SM) with
massive neutrinos and its new physics (NP) model extension in experiments of
the muon neutrino oscillation, following the pion decay $\pi^{+} \rightarrow
\mu^{+} + \nu_{\mu}$, is calculated. The stability of the estimation of the NP
charged current coupling constant $\varepsilon_{R}$ is analysed and the
robustness of this estimation is checked. It is shown that the upper bound on
the error probability of erroneous identification of the Standard Model with
its NP model extension has reached the significantly small value of
approximately $2.3 \times 10^{-6}$.
