1. The estimate of the population proportion is to be within plus or minus 0.04, with a 98% level of confidence. The best estimate of the population proportion is 0.25. How large a sample is required?
2. Forty-nine items are randomly selected from a population of 500 items. The sample mean is 40 and the sample standard deviation 9. Develop a 99% confidence interval for the population mean
3. A state meat inspector in Iowa has been given the assignment of estimating the mean net weight of packages of ground chuck labeled “3 pounds.” Of course, he realizes that the weights cannot be precisely 3 pounds. A sample of 36 packages reveals the mean weight to be 3.01 pounds, with a standard deviation of 0.03 pound.
• What is the estimated population mean?
• Determine a 95% confidence interval for the population mean
4. There are 20,000 eligible voters in York County, South Carolina. A random sample of 500 York County voters revealed 350 plan to vote to return Louella Miller to the state senate
• Construct a 99% confidence interval for the proportion of voters in the county who plan to vote for Ms. Miller. (Round your answers to 3 decimal places.)
• From this sample information, can you confirm she will be re-elected?
5. In a poll to estimate presidential popularity, each person in a random sample of 1,430 voters was asked to agree with one of the following statements
1. The president is doing a good job
2. The president is doing a poor job
3. I have no opinion
A total of 600 respondents selected the first statement, indicating they thought the president was doing a good job.
• Construct a 95% confidence interval for the proportion of respondents who feel the president is doing a good job. Round your answers to 3 decimal places.)
• Based on your interval in part (a), is it reasonable to conclude that a majority of the population believes the president is doing a good job?
6. Police Chief Edward Wilkin of River City reports 500 traffic citations were issued last month. A sample of 35 of these citations showed the mean amount of the fine was $54, with a standard deviation of $4.50
• Construct a 95% confidence interval for the mean amount of a citation in River City. (Round your answers to 2 decimal places. )
7. The proportion of public accountants who have changed companies within the last three years is to be estimated within 3%. The 99% level of confidence is to be used. A study conducted several years ago revealed that the percent of public accountants changing companies within three years was 22. (Round up your answers to the next whole number.)
• To update this study, the files of how many public accountants should be studied?
• How many public accountants should be contacted if no previous estimates of the population proportion are available?
8. A sample of 352 subscribers to Wired magazine shows the mean time spent using the Internet is 13.4 hours per week, with a sample standard deviation of 6.8 hours
• Find the 95% confidence interval for the mean time Wired subscribers spend on the Internet. (Round your answers to 2 decimal places.)
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