Question

20.4 Vaccine protection against cervical cancer. Most cases of cervical cancer are linked to a few strains of the human papillomavirus (HPV). The pharmaceutical company Merck developed a vaccine (Gardasil) against these HPV strains. Worldwide clinical trials followed young women 16 to 26 years of age after vaccination or administration of a placebo for two to four years for signs of HPV-caused cervical cancer. Of 8460 women given Gardasil, none developed HPV-caused cervical cancer. In contrast, 53 of the 8487 women given a placebo did.6

1. Why should we not use the large-sample confidence interval for these data?

2. Give the plus four 95% confidence interval for the difference between the two population proportions of women developing HPV-caused cervical cancer.

Answer 1