At the end of 1990, 1991, and 1992 the average prices of a share of stock in a money market portfolio were $34.83, $34.65 and $31.26 respectively. To investigate the average share price at the end of 1993, a random sample of 30 stocks was drawn and their closing prices on the last trading day of 1993 were observed with a mean of 33.583 and a standard deviation of 19.149. Estimate the average price of a share of stock in the portfolio at the end of 1993 with a 90% confidence interval.

A. [27.832 39.334]

B. [26.732 40.434]

C. [32.514 34.651]

D. [32.533 34.633]

E. [32.269 34.897]

The coffee/soup machine at the local bus station is supposed to fill cups with 6 ounces of soup. Ten cups of soup are brought with results of a mean of 5.93 ounces and a standard deviation of 0.13 ounces. Construct a 99% confidence interval for the true machine-fill amount.

A. [5.888 5.972]

B. [5.814 6.046]

C. [5.716 6.144]

D. [5.824 6.036]

E. [5.796 6.064]

An environmental group at a local college is conducting independent tests to determine the distance a particular make of automobile will travel while consuming only 1 gallon of gas. A sample of five cars is tested and a mean of 28.2 miles is obtained. Assuming that the standard deviation is 2.7 miles, find the 95% confidence interval for the mean distance traveled by all such cars using 1 gallon of gas.

A. [26.16 30.24]

B. [20.70 35.70]

C. [24.85 31.55]

D. [26.70 29.70]

E. [25.83 30.57]

A federal bank examiner is interested in estimating the mean outstanding defaulted loans balance of all defaulted loans over the last three years. A random sample of 20 defaulted loans yielded a mean of $67,918 with a standard deviation of $16,552.40. Calculate a 90% confidence interval for the mean balance of defaulted loans over the past three years.

A. [66,487 69,349]

B. [39,299 96,537]

C. [57,329 78,507]

D. [61,829 74,007]

E. [61,519 74,317]

In a manufacturing process, we are interested in measuring the average length of a certain type of bolt. Past data indicates that the standard deviation is .25 inches. How many bolts should be sampled in order to make us 95% confident that the sample mean bolt length is within .02 inches of the true mean bolt length?

A. 421

B. 423

C. 599

D. 601