At one SAT test site students taking the test for a second time volunteered to inhale supplemental oxygen for 10 minutes before the test. In fact, some received oxygen, but others (randomly assigned) were given just normal air. Test results showed that 42 of 66 students who breathed oxygen improved their SAT scores, compared to only 35 of 63 students who did not get the oxygen. Which procedure should we use to see if there is evidence that breathing extra oxygen can help test-takers think more clearly? - A school administrator wants to know if there is a difference in the mean math scores for two teachers at the same school. - A soda company wants to know what proportion of cans are damaged during the manufacturing process. It takes a random sample of cans and finds 13 of 462 cans are damaged.