The document discusses the chi-square test of independence, which determines if there is a relationship between two categorical variables. It explains that the chi-square test compares observed and expected category frequencies to assess if the null hypothesis of independence is true. An example calculates the chi-square test to see if gender and education level are related using a sample of 45 people's education data. The chi-square test value is greater than the critical value, so the null hypothesis of no relationship is rejected.