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# w11_CI_post - μ2 is the mean mortgage rate of banks in...

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(PS4, Q16) A sample of 20-year conventional mortgage rates at 35 randomly chosen banks in country A yields a mean rate of 7.61% and a standard deviation of 0.39%. A similar sample taken at 40 randomly chosen banks in country B has a mean rate of 7.43%, with a standard deviation of 0.56%. a. Construct a 95% confidence interval for μ1, the mean mortgage rate of banks in country A. b. How do you interpret this 95% confidence interval? c. If one wants to improve the accuracy by having the width of the confidence interval in (a) to be less than 0.1%. How many additional banks would have to be selected from country A? d. Construct a 95% confidence interval for the difference in the mean rates, μ1−μ2, where

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Unformatted text preview: μ2 is the mean mortgage rate of banks in country B. Do the data provide sufficient evidence (at = 5%) that the mean mortgage rates of the two countries are different? (Final 2000, Q2) The problem is to determine the proportion (p) of women among new digital video camera buyers. A statistician wants to choose a sample size such that the resulting 95% interval estimate for p has a margin of error (error bound) no larger than 0.05. (a) What sample size the statistician should choose? (b) What sample size the statistician should choose if it can be "safely" assumed that among new digital video camera buyers, at least 72.5% are men....
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w11_CI_post - μ2 is the mean mortgage rate of banks in...

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