We have measured the turbidity for a series of solutions of polymethylmethacrylate in 3-octanone (PMMA/3-OCT) with various polymer molecular weights. The obtained correlation length (xi) and the osmotic compressibility (chi) show power law dependence on both the reduced temperature epsilon = (T - T-c)/T-c and the degree of polymerization N of the polymer chains, i.e. xi similar to N(0.15)epsilon(-0.63) and chi similar to N(-0.06)epsilon(-1.23), with the associated scaling exponents in good agreement with theoretical predictions. When the results of the present experiment are combined with those from an earlier coexistence curve measurement [K.-Q. Xia, X.-Q. An, and W.-G. Shen, J. Chem. Phys. 105, 6018 (1996)], it is found that the concept of two-scale-factor universality applies to systems consist of the same polymer/solvent pair but with different molecular weights.