The U.S. Energy Information Association tracks the prices of regular unleaded gasoline in the United States each year. The table (p. 63) lists the average 1998 prices

(in cents) in each of a sample of 20 states.

a. Calculate the mean, median, and mode of this data set.

b. Eliminate the highest price from the data set and repeat part

a. What effect does dropping this mcasure- - -
ment have on the measures of central tendency calculated in part a?

c. Arrange the 20 prices in order from lowest to highest.
Next, eliminate ihe lowest two prices and the highest two prices from the data set and calculate the mean of the remaining prices. The result is called a 10%
trimmed meun, since it is calculated after dropping the highest 10% and the lowest 10% of the values in the data set. An advantage of the trimmed mean is that it is not as sensitive as the arithmetic mean to extreme observations in the data set.