Categorical Outcome Variable

So you have a categorical outcome variable. Question: What is/are your predictor variable(s)?

Example: You want to test the claim that less than 30% of an adult population got a flu shot this year.

Example: You want to know if the distribution of male and female students at a university differs across science and non-science majors.

Example: You are investigating what social and economic factors explain whether or not people use public transportation to commute to work.