  Theoretical uncertainties of various types are discussed for the
nucleon-deuteron elastic scattering observables at the incoming nucleon
laboratory energies up to 200 MeV. We are especially interested in the
statistical errors arising from uncertainties of parameters of a
nucleon-nucleon interaction. The obtained uncertainties of the differential
cross section and numerous scattering observables are in general small, grow
with the reaction energy and amount up to a few percent at 200 MeV. We compare
these uncertainties with the other types of theoretical errors like truncation
errors, numerical uncertainties and uncertainties arising from using the
various models of nuclear interaction. We find the latter ones to be dominant
source of uncertainties of modern predictions for the three-nucleon scattering
observables. To perform above mentioned studies we use the One-Pion-Exchange
Gaussian potential derived by the Granada group, for which the covariance
matrix of its parameters is known, and solve the Faddeev equation for the
nucleon-deuteron elastic scattering. Thus beside studying theoretical
uncertainties we also show a description of the nucleon-deuteron elastic
scattering data by the One-Pion-Exchange Gaussian model and compare it with
results obtained with other nucleon-nucleon potentials, including chiral
N$^4$LO forces from the Bochum-Bonn and Moscow(Idaho)-Salamanca groups. In this
way we confirm the usefulness and high quality of the One-Pion-Exchange
Gaussian force.
