At Franklin High school, 15% of the students play basketball and 4% of the students play baseball and basketball. What in the probability that a student plays baseball given that he or she play basketball?
4% of baseball players should play basketball , just because they play baseball it does not alter their probability of being a basketball player. However if you pick a student at random there is only 0.6% (15% x 4%) chance that they will play both sports.
In conclusion 4% of basketball players play baseball but only 0.6% of the entire student body play both sports.