  The NN scattering problem is usually analyzed in terms of partial waves and
the corresponding coupled channel phase-shifts and mixing angles, but the
available experiments induce correlations amongst the corresponding channels
with different quantum numbers. Based on the Granada-2013 database we analyze
the meaning and impact of those correlations taking into account both the
purely statistical ones reflecting the primary experimental data uncertainties
as well as the systematic ones exhibiting the ambiguities in the form of the
potential representing the unknown nuclear force for distances below 3fm. We
also ponder on the implications of fixing nuclear potentials by direct fits to
the phase-shifts stemming from a full fledged partial wave analysis (PWA)
inferred from experimental data.
