# Confidence Interval Problems (unknown S.D.)

#### Silverfox

##### New Member
Problem 1:
{Exercise 8.17}
The International Air Transport Association surveys business travelers to develop quality ratings for transatlantic gateway airports. The maximum possible rating is 10. Suppose a simple random sample of 50 business travelers is selected and each traveler is asked to provide a rating for the Miami International Airport. The ratings obtained from the sample of 50 business travelers follow.

6 4 6 8 7 7 6 3 3 8 10 4 8

7 8 7 5 9 5 8 4 3 8 5 5 4

4 4 8 4 5 6 2 5 9 9 8 4 8

9 9 5 9 7 8 3 10 8 9 6

Develop a 95% confidence interval estimate of the population mean rating for Miami (to 2 decimals).

95% Confidence:

I have n=50, added up the numbers and got M=6.34

Really have no idea where to go from here.

Problem 2:
{Exercise 8.21}
Complaints about rising prescription drug prices caused the U.S. Congress to consider laws that would force pharmaceutical companies to offer prescription discounts to senior citizens without drug benefits. The House Government Reform Committee provided data on the prescription cost for some of the most widely used drugs (Newsweek, May 8, 2000). Assume the following data show a sample of the prescription cost in dollars for Zocor, a drug used to lower cholesterol.

110 112 115 99 100 98 104 126

Given a normal population, what is the 95% confidence interval estimate of the population mean cost for a prescription of Zocor (to 2 decimals)?

95% Confidence:

I have n=8 & M= 108
unsure what to do

Problem 3:
{Exercise 8.27}
Annual starting salaries for college graduates with degrees in business administration are generally expected to be between $30,000 and$45,000. Assume that a 95% confidence interval estimate of the population mean annual starting salary is desired. What is the planning value for the population standard deviation (0 decimals)?

How large a sample should be taken if the desired margin of error is as shown below (0 decimals)?

a. $500? b.$200?

c. \$100?

No idea whatsoever for the above problem