We compare resonant Raman Scattering (RS) and Photoluminescence (PL) measurements on a spin polarized two-dimensional electron gas embedded in a CdMnTe quantum well. RS by single particle excitations furnishes the Fermi energy E-F, which is more than E-F extracted from PL. Spin-flip RS spectra at wavevector q similar to 0, show the one electron spin-flip energy, Z*. Magneto-PL spectra give only Z. If we neglect mass renormalization, the spin polarization degree, C obtained from the PL lineshape is different from those derived from spin-flip RS. We attribute the discrepancies in E-F and zeta to the renormalized mass.