More about Confidence Intervals Answers

A college professor would like to estimate the proportion of students who pull an "all-nighter,” meaning they study all night for an upcoming exam. She selects a random sample of 100 students from her large college and finds that the 99% confidence interval for the true proportion of students who have pulled an all-nighter to be 0.48 to 0.62. If the professor had randomly selected 50 students rather than 100 students, what effect would this have had on the width of the interval?

The maker of a cell phone screen protector would like to estimate the proportion of customers who file a warranty claim. To do so, they select a random sample of 200 customers and determine that the 96% confidence interval for the true proportion of customers who file a warranty claim to be 0.15 to 0.28. Which of the following would decrease the margin of error?

An animal rescue agent wanted to estimate the true proportion of all animals in shelters that are adopted each month. To do so, she selects a random sample of 100 animals and determines that the 95% confidence interval for the true proportion of animals adopted each month is between 0.12 and 0.24. Which of these statements is a correct interpretation of the confidence level?

A farmer of a large apple orchard would like to estimate the true mean number of suitable apples produced per tree. He selects a random sample of 40 trees from his large orchard and determines with 95% confidence that the true mean number of suitable apples produced per tree is between 375 and 520. Which of these statements is a correct interpretation of the confidence level?

Heather runs a successful lawn-mowing business. She would like to estimate the true mean amount of time it takes for her employees to mow a lawn. To do so, she selects a random sample of 30 customers and records the time it takes the employees to mow their lawns. The 90% confidence interval for the true mean time it takes her employees to mow a lawn is 40 to 55 minutes. Which of these statements is a correct interpretation of the confidence level?

A college professor would like to estimate the proportion of students who pull an "all-nighter,” meaning they study all night for an upcoming exam. She selects a random sample of 100 students from her large college and finds that the 99% confidence interval for the true proportion of students who pull an all-nighter is 0.48 to 0.62. Which of these statements is a correct interpretation of the confidence level?

A farmer of a large apple orchard would like to estimate the true mean number of suitable apples produced per tree. He selects a random sample of 40 trees from his large orchard and determines with 95% confidence that the true mean number of suitable apples produced per tree is between 375 and 520 apples. If the farmer had selected 160 trees from his large apple orchard rather than 40 trees, what effect would this have had on the margin of error?

An animal rescue agent wanted to estimate the true proportion of all animals in shelters that are adopted each month. To do so, she selects a random sample of 100 animals that were in shelters last month and determines that the 95% confidence interval for the true proportion of animals adopted each month is between 0.12 and 0.24. Which of the following would decrease the margin of error?

Sam runs a large chain of car repair shops. He pays his employees for 8 hours of work each day. The employees have to log the amount of time they spend working on each job, which results in a number of billable hours for each employee each day. Sam would like to estimate the mean number of billable hours for the large number of employees at the company. To do so, he selects a random sample of 10 employees and asks them how many billable hours they tend to have each day. From their responses, he constructs a 95% confidence interval for the true mean number of billable hours for all employees in the company. Which of the following may have an impact on the confidence interval, but is not accounted for by the margin of error?

An animal rescue agent wanted to estimate the true proportion of all animals in shelters that are adopted each month. To do so, she selects a random sample of 100 animals that were in shelters last month and determines that the 95% confidence interval for the true proportion of animals adopted is between 0.12 and 0.24. This interval has a margin of error of 0.06. Which of the following can be accounted for by the margin of error?