In a large clinical trial, 396,805 children were randomly assigned to two groups. The treatment group consisted of 199,968 children given a vaccine for a certain disease, and 38 of those children developed the disease. The other 196,837 children were given a placebo, and 137 of those children developed the disease. Consider the vaccine treatment group to be the first sample. A. Assume that a 0.01 significance level will be used to test the claim that p1 less than p2. Which is better: A hypothesis test or a confidence interval?
B. If a 0.01 significance level is to be used to test the claim that p 1less thanp 2, what confidence level should be used?
C. If the claim in part (c) is tested using this sample data, we get this confidence interval: -0.000417 less than p1 - p2 less than -0.000168. What does this confidence interval suggest about the claim?
Because the confidence interval___(does not contain or contains)___(0, the pooled sample proportion, the critical value, or the significance value) there(appears to be or does not appear to be) a significant difference between the two proportions. Because the confidence interval consists___(only of values greater than, of values both less than and greater than, or only of values less than)(0, the significance value, critical value, or the pooled sample proportion) it appears that the first proportion is(greater than, less than, or not significantly different from the second proportion). There is(sufficient, or insufficient) evidence to support the claim that the rate of polio is less for children given the vaccine than it is for children given a placebo.