Chemical shifts provide detailed information about non-covalent structure, solvent interactions, ionization constants, ring orientations, hydrogen bond interactions, and other phenomena. Since different chemical shift data sets are not necessarily comparable without corrections or adjustments, the applicability of statistical analysis of NMR chemical shifts to biomolecules has so far been limited. We use the term "congruent" to describe data sets that can be directly used for statistical analysis after proper adjustments. Congruence problems in chemical shift analysis can occur at three...