In this sub-competency, we will build on the notations begun in sub-competency 11, where we looked at comparing two groups or populations. We will also be using what you learned about two-way tables in sub-competency 6 as well. You may wish to review these sections before beginning here.

In sub-competency 11, we compared two groups of numerical data, two populations or two treatment groups. However, this was a way to compare quantitative variables. What if instead we wished to compare two categorical variables? To do this we will need a new test and a new distribution, called the chi-squared test or *x*-squared test.