In its Fuel Economy Guide for 2014 model vehicles, the Environmental Protection
ID: 3204540 • Letter: I
Question
In its Fuel Economy Guide for 2014 model vehicles, the Environmental Protection Agency gives data on 1160 vehicles. There are a number of high outliers, mainly hybrid gas-electric vehicles. If we ignore the vehicles identified as outliers, however, the combined city and highway gas mileage of the other 1134 vehicles is approximately Normal with mean 22.2 miles per gallon (mpg) and standard deviation 5.2 mpg.
The quartiles of any distribution are the values with cumulative proportions 0.25 and 0.75. They span the middle half of the distribution. What are the quartiles of the distribution of gas mileage? (Round your answers to two decimal places.)
Explanation / Answer
ans=
Quartiles. In the table, seek P = 0.75, it shows z = 0.674
Since the distribution is symmetrical, the P = 0.25
would be at z = -0.674.
Gas mileage = 22.2 +/- (5.2)(0.674) = 18.69and 25.7
(first quartile 18.69, third quartile 25.7)