Is this convincing? You are planning to test a vaccine for a virus that now has no vaccine. Since the disease is usually not serious, you will expose 100 volunteers to the virus. After some time, you will record whether or not each volunteer has been infected.

(a) Explain how you would use these 100 volunteers in a designed experiment 518 CHAPTER 23 Use and Abuse of Statistical Inference to test the vaccine. Include all important details of designing the experiment

(but don’t actually do any random allocation).

(b) You hope to show that the vaccine is more effective than a placebo. State H0 and Ha. (Notice that this test compares two population proportions.)

(c) The experiment gave a P-value of 0.15. Explain carefully what this means.

(d) Your fellow researchers do not consider this evidence strong enough to recommend regular use of the vaccine. Do you agree?

The following exercises require carrying out the methods described in the optional sections of Chapters 21 and 22.