Corrections are derived for the calculation of the second and fourth moments of magnetic resonance lines from experimental data, obtained by using the low-frequency modulation method. The results for 0\ifmmode^\circ\else\textdegree\fi{} phase shift between field modulation and the lock-in reference are ${〈\ensuremath{\Delta}{{\ensuremath{\omega}}_{\mathrm{exp}}}^{2}〉}_{\mathrm{Av}}={〈\ensuremath{\Delta}{\ensuremath{\omega}}^{2}〉}_{\mathrm{Av}}+\frac{1}{3}{{\ensuremath{\omega}}_{M}}^{2}+\frac{1}{4}{(\ensuremath{\gamma}{H}_{M})}^{2},$ ${〈\ensuremath{\Delta}{{\ensuremath{\omega}}_{\mathrm{exp}}}^{4}〉}_{\mathrm{Av}}={〈\ensuremath{\Delta}{\ensuremath{\omega}}^{4}〉}_{\mathrm{Av}}+{〈\ensuremath{\Delta}{\ensuremath{\omega}}^{2}〉}_{\mathrm{Av}}[2{{\ensuremath{\omega}}_{M}}^{2}+\frac{3}{2}{(\ensuremath{\gamma}{H}_{M})}^{2}]+\frac{1}{5}{{\ensuremath{\omega}}_{M}}^{4}+\frac{3}{4}{{\ensuremath{\omega}}_{M}}^{2}{(\ensuremath{\gamma}{H}_{M})}^{2}+\frac{1}{8}{(\ensuremath{\gamma}{H}_{M})}^{4}.$