These tests are based on data collected in the form of a contingency table of 2 traits, trait X and trait Y, the former having and the latter categories, so the resulting table has rows and columns. Therefore, we can speak of the 2×2 chi-square test (for tables with two rows and two columns) or the RxC chi-square test (with multiple rows and columns)).
We can read the details of the chi-square test of the two features here:
The additional assumption for the :
– observed frequencies in a contingency table,
– expected frequencies in a contingency table.
Hypotheses in the meaning of independence:
Multiple column comparisons (RxC).