18. Thirty fast-food restaurants including Wendy’s, McDonald’s, and Burger King were visited during the summer of 2000 (The Cincinnati Enquirer, July 9, 2000). During each visit, the customer went to the drive-through and ordered a basic meal such as a “combo” meal or a sandwich, fries, and shake. The time between pulling up to the menu board and receiving the filled order was recorded. The times in minutes for the 30 visits are as follows:

0.9 1.0 1.2 2.2 1.9 3.6 2.8 5.2 1.8 2.1 6.8 1.3 3.0 4.5 2.8 2.3 2.7 5.7 4.8 3.5 2.6 3.3 5.0 4.0 7.2 9.1 2.8 3.6 7.3 9.0

a. Provide a point estimate of the population mean drive-through time at fast-food restaurants.

b. At 95% confidence, what is the margin of error?

c. What is the 95% confidence interval estimate of the population mean?

d. Discuss skewness that may be present in this population. What suggestion would you make for a repeat of this study?