Low-frequency Raman scattering of water-ethylene glycol oligomer (EGO) binary mixtures have been carried out. Reduced spectra of mixtures were decomposed into a linear combination of pure water and neat EGO spectra. The superposed spectra systematically deviate from the measured spectra of mixtures below 80 cm(-1). Integrated intensity of the difference between obtained spectrum and superposed spectrum, Delta(chi"), depends on both the concentration and the unit numbers of EGO. Small Delta(chi") and nonlinear concentration dependence of the coefficients of linear combination are related to the cooperative motions of EGO and water molecules. (C) 2003 American Institute of Physics.