  Theoretical predictions need quantified uncertainties for a meaningful
comparison to experimental results. This is an idea which presently permeates
the field of theoretical nuclear physics. In light of the recent progress in
estimating theoretical uncertainties in ab initio nuclear physics, we here
present and compare methods for evaluating the statistical part of the
uncertainties. A special focus is put on the (for the field) novel method of
Lagrange multipliers (LM). Uncertainties from the fit of the nuclear
interaction to experimental data are propagated to a few observables in
light-mass nuclei to highlight any differences between the presented methods.
The main conclusion is that the LM method is more robust, while covariance
based methods are less demanding in their evaluation.
