A sample of 200 students at a Big-Ten university was taken after the midterm to ask
them whether they went bar hopping the weekend before the midterm or spent the
weekend studying, and whether they did well or poorly on the midterm. The following table contains the result.

Did Well in Midterm Did Poorly in Midterm
Studying for Exam 80 20
Went Bar Hopping 30 70

Of those who did well on the midterm in the sample,
percent of them went bar hopping the weekend before the midterm.