Static dielectric permittivity in the nematic phase of a Nematogenic compound 4-4' Dipentylazoxy benzene had been measured at various temperatures using a sensitive LCR meter. Using these data, the dipole moment associated with the molecule is calculated. The validity of this approach is discussed by comparing the order parameter 'S' obtained from the Refractive index with the values of 'S' computed from the predictions of the mean field theories. Boardwijk's theory is applied here with appropriate molecular parameters to compute dipole-dipole correlation factor.