Question: An article in Time magazine (Gorman, 6 February 1995) reported that an advisory panel recommended that the Food and Drug Administration (FDA) allow an experimental AIDS vaccine to go forward for testing on 5000 volunteers. The vaccine was developed by Jonas Salk, who developed the first effective polio vaccine. The AIDS vaccine was designed to boost the immune system of HIV infected individuals and had already been tested on a small number of patients, with mixed results but no apparent side effects.

a. In making its recommendation to the FDA, the advisory panel was faced with a choice similar to that in hypothesis testing. The null hypothesis was that the vaccine was not effective and therefore should not be tested further, whereas the alternative hypothesis was that it might have some benefit. Explain the consequences of a type 1 and a type 2 error for the decision the panel was required to make.

b. The chairman of the panel, Dr. Stanley Lemon, was quoted as saying, "I'm not all that excited about the data I've seen [but] the only way the concept is going to be laid to rest is really to try [the vaccine] in a large population" (p. 53). Explain why the vaccine should be tested on a larger group, when it had not proven effective in the initial tests on a small group.