We reanalyze deep inelastic scattering data of BCDMS Collaboration by
including proper cuts of ranges with large systematic errors. We perform also
the fits of high statistic deep inelastic scattering data of BCDMS, SLAC, NM
and BFP Collaborations taking the data separately and in combined way and find
good agreement between these analyses. We extract the values of both the QCD
coupling constant \alpha_s(M^2_Z) up to NLO level and of the power corrections
to the structure function F_2. The fits of the combined data for the nonsinglet
part of the structure function F_2 predict the coupling constant value
\alpha_s(M^2_Z) = 0.1174 \pm 0.0007 (stat) \pm 0.0019 (syst) \pm 0.0010
(normalization) (or QCD parameter \Lambda^{(5)}_{MSbar} = 204 \pm 25 (total
exper.err.) MeV). The fits of the combined data for both: the nonsinglet part
and the singlet one, lead to the values \alpha_s(M^2_Z) = 0.1177 \pm 0.0007
(stat) \pm 0.0021 (syst) \pm 0.0009 (normalization) (or QCD parameter
\Lambda^{(5)}_{MSbar} = 208 \pm 27 (total exper.err.) MeV). Both above values
are in very good agreement with each other. We estimate theoretical
uncertainties for \alpha_s(M^2_Z) as +0.0047 and -0.0057 from fits of the
combine data, when complete singlet and nonsinglet Q^2 evolution is taken into
account.Comment: 47 pages, 14 figures, late
