We report the final results of a study of the psi ( 3770 ) meson using a data sample collected with the KEDR detector at the VEPP-4M electron-positron collider. The data analysis takes into account interference between the resonant and nonresonant D D macr production, where the latter is related to the nonresonant part of the energy-dependent form factor F D . The vector dominance approach and several empirical parameterizations have been tried for the nonresonant F D N R ( s ) . Our results for the mass and total width of psi ( 3770 ) are M = 3779.2 - 1.7 + 1.8 - 0.7 + 0.5 - 0.3 + 0.3 MeV , Gamma = 24.9 - 4.0 + 4.6 - 0.6 + 0.5 - 0.9 + 0.2 MeV , where the first, second and third uncertainties are statistical, systematic and model, respectively. For the electron partial width two possible solutions have been found: ( 1 ) Gamma e e = 154 - 58 + 79 - 9 + 17 - 25 + 13 eV , ( 2 ) Gamma e e = 414 - 80 + 72 - 26 + 24 - 10 + 90 eV . Our statistics are insufficient to prefer one solution to another. The Solution (2) mitigates the problem of non- D D macr decays but is disfavored by potential models. It is shown that taking into account the resonance-continuum interference in the near-threshold region affects resonance parameters, thus the results presented cannot be directly compared with the corresponding PDG values obtained ignoring this effect.