Comparison of accuracy of the methods of total counting, total
counting in optimum zones of spectrum and maximum likelihood with
reference to a problem of an estimation of activity of isotopes 137Cs,
134Cs and 222Rn from their gamma-radiation spectra with small
statistics in spectrum channels and with a known background is spent.
It is shown, that the application for the spectra analysis of the
maximum likelihood method gives a gain 10 - 20 % in accuracy in
comparison with the methods of total counting and total counting in
optimum zones of spectrum.
