QUESTION 1

The health of the bear population in Yellowstone National Park is monitored by periodic measurements taken from anesthetized bears. A sample of 49 bears has a mean weight of 182 pounds. If the population standard deviation is assumed to be 121.6 pounds, find a 95% confidence interval for the true mean weight of the Yellowstone bear population. Round off to the nearest whole pound.

A. (148, 216) pounds

B. (165, 199) pounds

C. (60, 304) pounds

D. (126, 238) pounds

E. (177, 187) pounds

Question 2

Referring to Question 1: The margin of error of the confidence interval, rounded off to the nearest whole pound, is:

Select one:

A. 122 pounds

B. 17 pounds

C. 34 pounds

D. 68 pounds

E. 56 pounds

Question 3

Referring to Question 1: Find the sample size necessary for a 95% confidence interval if the margin of error can not exceed 20 pounds.

A. n = 12

B. n = 37

C. n = 101

D. n = 142

E. n = 143

Question 4

A study was conducted to estimate hospital costs for accident victims who wore seat belts. It is believed the population is normally distributed, but the population standard deviation is not known.

A random sample of 20 cases has a mean of $9004. with a standard deviation of $5644. Find a 98% confidence interval for the true mean hospital cost. Round off to the nearest whole dollar.

A. ($6063, $11945)

B. ($5813, $12195)

C. ($5799, $12209)

D. ($8287, $9721)

E. ($6362, $11646)

Question 5

Referring to Question 4: The width of the confidence interval, rounded off to the nearest whole dollar, is:

A. $5284.

B. $6410.

C. $3205.

D. $5882.

E. $1434.

Question 6

Brilliant Battery Company produces heavy-duty batteries for use in emergency generators. Battery life is normally distributed and the population standard deviation is known to be 10.2 months. Using a random sample of 25, with a sample mean of 55 months, the 95% confidence interval for the true mean life of the batteries is determined to be: (51, 59) months (rounded off to the nearest whole month).

How can Brilliant Battery Company's quality control manager increase the precision of the confidence interval, but without increasing the dollar cost of determining the confidence interval?

A. Increase the confidence level from 95% to 99%.

B. Increase the sample size.

C. Reduce the sample size.

D. Reduce the confidence level from 95% to 90%.

E. It is not possible to increase the precision without increasing the dollar cost.

Question 7

A sample of 15 axe guitars has a mean price of $377.00. A 95% confidence interval for the true mean price, derived from this sample, has a margin of error of $83.00. What are the upper and lower limits of the confidence interval?

A. ($211. , $543.)

B. ($331. , $423.)

C. ($294. , $460.)

D. ($227. , $527)

E. Can't be determined from the information given.

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