Concept explainers
In each of Exercises 12.128–12.131, use the two-proportions plus-four z-interval procedure to find the required confidence interval. Interpret your results.
12.128 Confidence in Banks. Since 1973, Gallup has asked Americans how much confidence they have in a variety of U.S. institutions. One question asked of those polled is whether they have a great deal of confidence in banks. In 2007, of a random sample of 1008 adult Americans, 413 said yes; and, in 2013, of a random sample of 1529 adult Americans, 398 said yes. For the two years, find and interpret a 95% confidence interval for the difference between the percentages of adult Americans who had a great deal of confidence in banks.
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Chapter 12 Solutions
Introductory Statistics (10th Edition)
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