Statistical analysis of relative quantities in medicine

The purpose of the work is to summarize information on the basic methods of data analysis presented at nominal scales. The methodology for describing relative values is presented, and the criteria for comparing groups in this case are also considered. In particular, the conditions and algorithms for using the Pearson  2 test, the Fisher exact test, the odds ratio, the relative risk, and the McNemar test are presented. Practical examples are considered by all criteria. Conclusions . It is determined that Pearson test  2 for comparison of independent samples is recommended for statistical analysis of medical research results, if in all cells the number is greater than 10; Fisher's exact test to compare small independent samples; odds ratio for assessing relative risk in case studies; relative risk for prospective research analysis; McNemar test for comparison of dependent samples.