  Commensurate scale relations relate observables to observables and thus are
independent of theoretical conventions, such as the choice of intermediate
renormalization scheme. The physical quantities are related at commensurate
scales which satisfy a transitivity rule which ensures that predictions are
independent of the choice of an intermediate renormalization scheme. QCD can
thus be tested in a new and precise way by checking that the observables track
both in their relative normalization and in their commensurate scale
dependence. For example, the radiative corrections to the Bjorken sum rule at a
given momentum transfer $Q$ can be predicted from measurements of the e+e-
annihilation cross section at a corresponding commensurate energy scale $\sqrt
s \propto Q,$ thus generalizing Crewther's relation to non-conformal QCD. The
coefficients that appear in this perturbative expansion take the form of a
simple geometric series and thus have no renormalon divergent behavior. We also
discuss scale-fixed relations between the threshold corrections to the heavy
quark production cross section in e+e- annihilation and the heavy quark
coupling $\alpha_V$ which is measurable in lattice gauge theory.
