The calculations of Chasmar and Stratton [R. P. Chasmar and R. Stratton, J. Electronic and Control7, 52 (1959)] for the determination of the maximum thermoelectric figure of merit are extended for the case of acoustical scattering. Graphical data are presented for the determination of the material parameter, the optimum values of several quantities, and the degradation of the figure of merit for nonoptimum conditions. The variations of the Seebeck coefficient and the electrical conductivity computed from exact statistics are compared with experimental results for several alloys of thermoelectric interest. Good agreement is found except for high electrical conductivities. Other anomalies are noted.