a. You want to test whether there is an association between a categorical variable and a numerical variable. For example, you want to test whether there is an association between type of apartment (studio, one-bedroom, or two-bedroom) and monthly rent.

b. You want to test whether the means of a numerical variable are different for two possible values of a categorical variable. For example, you want to test whether the mean income of paramedics is the same for male and female paramedics.