Question: The drug AZT was the first drug that seemed effective in delaying the onset of AIDS in people infected with HIV. Evidence for AZT's effectiveness came from a large double blind, randomized comparative experiment. The subjects were 1300 HIV-positive volunteers who had not yet developed AIDS. The study assigned 435 of the subjects at random to take 500 milligrams of AZT each day and another 435 to take a placebo. (The others were assigned to a higher dose of AZT, but we will compare only the first two groups.) At the end of the study, 42 of the placebo subjects and 11 of the AZT subjects had developed AIDS.
(a) What is the relative risk for developing AIDS for the AZT group compared with the placebo group? Please use 4 decimal places.