The fullest utilization of harvested grain is an important task of agricultural production. During separation of seed grain from grain heap a large amount of grain impurities (feeble and crushed grain) being a valuable animal feed is lost. One of the effective methods of separation of grain impurities from light waste is the fractionation on aerodynamic properties. When developing and improving the devices for fractionation of light waste by means of airflow, it is necessary to carry out a large number of experiments, which is associated with time, energy and material consumption. Mathematical modeling allows to minimize the number of experiments. Before applying a mathematical model in designing of technical devices, it is necessary to assess its adequacy. The article presents the assessment of adequacy of the results of mathematical modeling of light waste fractionation process to the experimental results. Qualitative assessment of adequacy is carried out by determining whether the results of mathematical modeling are within the tolerance range of experimental data; quantitative assessment is carried out by means of statistical hypotheses testing. The results of theoretical calculations draw one sample, the results of experiments draw another. Two statistical hypotheses are considered. Each of the hypotheses is tested at 0.05 of significance level. The hypothesis that both of received samples belong to the same parent population is tested with the use of the sign test. As a result of research, the hypothesis is accepted on the selected significance level. Then a regression model is developed for each of the samples, and using the Chow test the hypothesis about the coincidence of constructed regression models is tested. As a result of research, the second hypothesis is also accepted at 0.05 of significance level. The considered mathematical model can be used in the design of technical devices for fractionation of light waste.