  Deep inelastic scattering data on the F_2 structure function provided by the
BCDMS, SLAC and NMC collaborations are analyzed in the non-singlet
approximation with the analytic and "frozen" modifications of the strong
coupling constant featuring no unphysical singularity (the Landau pole).
Improvement of agreement between theory and experiment, with respect to the
case of the standard perturbative definition of alpha_s considered recently, is
observed and the behavior of the higher twist terms in the
next-to-next-to-leading-order is found to be confirming earlier studies on the
subject.
