The influence of correlation effects on the density of states deduced from field-effe6t and capacitance-voltage measurements are considered. A positive Hubbard U is required to account for the observed Curie-law behaviour of the magnetic suszeptibility. Hence, statistics of correlated electrons have to be used rather than Fermi-statistics to calculate the density of states distribution function g(E) from the measured charge density. Within this model g(E) 'differs appreciably from previously published "field effect" densities.