You are conducting an experiment. In a large elementary school, you select two age-matched groups of students. Group 1 follows a normal schedule. Group 2 spends 30 minutes a day in art class in addition to their other classes. You want to test whether learning art makes a student less likely to get in trouble. You consider a student in trouble if he or she was sent to the principal's office at any time during the year. The data you collect would BEST be analyzed by which of the following?