Exam 8: Interval Estimation

A bank manager wishes to estimate the average waiting time for customers in line for tellers. A random sample of 50 times is measured and the average waiting time is 5.7 minutes. The population standard deviation of waiting time is 2 minutes. Which Excel function would be used to construct a confidence interval estimate?

We can use the normal distribution to make confidence interval estimates for the population proportion, p, when _____.

The t distribution should be used whenever _____.

The confidence associated with an interval estimate is called the _____.

The margin of error in an interval estimate of the population mean is a function of all of the following EXCEPT _____.

As the number of degrees of freedom for a t distribution increases, the difference between the t distribution and the standard normal distribution _____.

As the degrees of freedom increase, the t distribution approaches the _____ distribution.

A manufacturer wants to estimate the proportion of defective items that are produced by a certain machine. A random sample of 50 items is selected. Which Excel function would NOT be appropriate to construct a confidence interval estimate?

If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be _____.

The margin of error in an interval estimate of the population mean is a function of all of the following EXCEPT _____.

A random sample of 25 employees of a local company has been measured. A 95% confidence interval estimate for the mean systolic blood pressure for all company employees is 123 to 139. Which of the following statements is valid?

A sample of 26 elements from a normally distributed population is selected. The sample mean is 10 with a standard deviation of 4. The 95% confidence interval for μ is _____.

If we change a 95% confidence interval estimate to a 99% confidence interval estimate, we can expect the _____.

As the degrees of freedom increase, the t distribution approaches the _____ distribution.

The mean of the t distribution is _____.

A reporter for a student newspaper is writing an article on the cost of off-campus housing. A sample was selected of 10 one-bedroom units within a half-mile of campus and the rents paid. The sample mean is $550 and the sample standard deviation is $60.05. Provide a 95% confidence interval estimate of the mean rent per month for the population of one-bedroom units within a half-mile of campus. Assume this population is normally distributed.

A random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population mean is _____.

A random sample of 36 magazine subscribers is selected to estimate the mean age of all subscribers. The data follow. Use Excel to construct a 90% confidence interval estimate of the mean age of all of this magazine's subscribers. Subscriber Age Subscriber Age Subscriber Age 1 39 13 40 25 38 2 27 14 35 26 51 3 38 15 35 27 26 4 33 16 41 28 39 5 40 17 34 29 35 6 35 18 46 30 37 7 51 19 44 31 33 8 36 20 44 32 41 9 47 21 43 33 36 10 28 22 32 34 33 11 33 23 29 35 46 12 35 24 33 36 37

For which of the following values of p is the value of P(1 − p) maximized?

A survey of 40 students at a local college asks, "Where do you buy the majority of your books?" The responses fell into three categories: "at the campus bookstore," "on the Internet," and "other." The results follow. Use Excel to estimate the proportion of the college students who buy their books on the Internet. $\text { Where Most Books Bought }$ bookstore bookstore Internet other Internet other bokstore other bookstore bookstore bookstore bookstore bookstore other bokstore bookstore bookstore Internet Internet other other other other other other other Internet bookstore other other Internet other bookstore bookstore other bookstore Internet Internet bother bookstore