Any experimental or clinical study can be considered complete only when using a specific method or methods of statistical analysis of the data obtained. Moreover, selection of a specific statistical method is determined by the purpose and objectives of the study, as well as the nature of the characteristics used for the description of the studied object. The use of mathematical statistics methods which are not correct for a specific study may lead to a distortion of the significance of the results obtained. This paper provides a comparative assessment of various statistical methods for evaluation of the results obtained in a clinical study on the efficacy of the pineal peptide preparation Epithalamin. Long-term experimental studies of Epithalamin revealed its ability to not only increase the lifespan of various animal species, but also to inhibit spontaneous carcinogenesis. The results of these studies served as the basis for a clinical study on the effectiveness of Epithalamin for preventing the development of age-related pathology in the elderly. The article discusses in comparative aspects such issues as the problem of multiple comparisons, the use of the Bonferroni correction as a method for a more accurate estimation of differences, and the use of the Bayes factors. Controversial issues on the P-value or the probability value, which is used for hypothesis testing and the legitimacy of using the value p