In September 2004, the pharmaceutical company Merck withdrew its blockbuster drug rofecoxib (a painkiller, better known under its brand name, Vioxx) from the worldwide market amid concerns about its safety. By that time, millions of people had used the drug. In a 2000 study comparing rofecoxib to a control group (naproxen), it was mentioned that “Myocardial infarctions were less common in the naproxen group than in the rofecoxib group (0.1 percent vs. 0.4 percent; 95 percent confidence interval for the difference, 0.1 to 0.6 percent; relative risk, 0.2; 95 percent confidence interval, 0.1 to 0.7)”.
a. Find and interpret the difference of proportions between the naproxen and rofecoxib groups.
b. Interpret the stated relative risk.
c. In this study, myocardial infarctions were how much more likely to occur in the rofecoxib group than in the naproxen group?