Question: The standard treatment of ovarian cancer by the chemicals cytoxan and cisplatin substantially shrinks or eliminates tumors in about 60% of patients. Taxol, derived from the bark of yew trees, is expected to improve upon those response rates. If a clinical trial is conducted to randomly assign patients to the standard chemicals or to taxol, with equal numbers in each group, how large a sample size would be needed to distinguish a 75% response rate for taxol, at 95% confidence? (Data from "Yew Drugs Show Their Mettle," Science News 143 (May 29, 1993): 344.