QUESTION 1

1. Which of the following is the best definition of a confidence interval for ?

a. A confidence interval for is an interval where is guaranteed to be between the lower and upper limits.

b.A confidence interval for is an interval of the form L < < U, where the endpoints L and U are computed from the sample data.

c.A confidence interval for can only be one-sided.

d.A confidence interval for can only be two-sided.

QUESTION 2

1. You can calculate a confidence interval for , if you have:

a.	The confidence level that you are using (in order to calculate the z value), the sample mean, sample size, and population standard deviation
b.	The confidence level and the sample mean
c.	The confidence level, the population mean, and the sample size
d.	The confidence level, the population mean, the sample size, and the population standard deviation.

QUESTION 3

1. Historical data has indicated that the time it takes to complete one re-conditioning on a certain part is normally distributed and that= 2 min. A random sample of 9 specimens was tested, and the average time was found to be 98 min. Find a 95% confidence interval on the time for re-conditioning. Please enter only the lower limit answer in the box. Round your answer to three significant digits.

QUESTION 4

1. The life in hours of a 75-watt light bulb is known to be normally distributed with =25 hours. A random sample of 20 bulbs has a mean life of 1014 hours. Construct a 99% two-sided confidence interval on the mean life. What are the lower and upper limits of this interval?

a.	999.60 & 1048.40
b.	999.60 & 1028.40
c.	969.60 & 1028.40
d.	1003.04 & 1024.96

QUESTION 5

1. Using the data in question 4, construct a 95% lower bound on the mean life.

a.	996.4
b.	999.8
c.	1001.8
d.	1004.80