Question 18 (5 points) A utlility company sampled 494 customers, and finds that

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Question 18 (5 points) A utlility company sampled 494 customers, and finds that 110 of them had a discrpancy on their service bill, what is the upper bound for the 99% confidence interval for the proportion of customers with a discrepancy on their service bill? Round to three decimal places (for example: 0.419). Write only a number as your answer Your Answer: Answer Save Question 19 (5 points) A pollster wants to construct a 95% confidence interval for the proportion of adults who believe that economic conditions are getting better. A Gallup poll taken in July 2010 estimates this proportion to be 0.33. Using this estimate, what sample size is needed so that the confidence interval will have a margin of error of 0.045? Write only an integer as your answer Your Answer: Answer Save Question 20 (5 points) A researcher wants to construct a 99% confidence interval for the proportion of people who changed jobs in the past year. What sample size is needed so that the confidence interval will have a margin of error of 0.072? Write only an integer as your answer Your Answer: Answer

Explanation / Answer

z for 99% confidence is 2.765

p is 110/494 =0.22267

thus answer is p+z*s where s=sqrt(p*(1-p)/N)

thus 0.22267+2.765*sqrt(0.22267*(1-0.22267)/494)=0.274426539

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