Question: Refer to Example II. A 95% confidence interval for the difference in proportions of children who would get ear infections with placebo compared to with xylitol was 0.02 to 0.226. On the basis of this information, specify a one-sided 97.5% confidence interval and explain how you would use it to test H0: p1 - p2 = 0 versus Ha: p1 - p2. 0 with a = .025.
Example II: Ear Infections and Xylitol For Example I, children were randomly assigned to take xylitol or a placebo in a clinical trial done to see if xylitol might reduce the risk of getting ear infections. The Minitab output on page 480 of Chapter 12 provides 0.036 as a lower bound for a one-sided 95% confidence interval for the difference between population proportions getting ear infections for placebo versus xylitol.
Example I: The Prevention of Ear Infections On the basis of its biochemical properties, Finnish researchers hypothesized that regular use of the sweetener xylitol might be useful for preventing ear infections in preschool children and carried out a study to test this hypothesis (Uhari, 1998).