Fast Service Truck Lines uses the Ford Super Duty F-750 exclusively. Management made
a study of the maintenance costs and determined the number of miles traveled during
the year followed the normal distribution. The mean of the distribution was 60,000 miles
and the standard deviation 2,000 miles.
a. What percent of the Ford Super Duty F-750s logged 65,200 miles or more?
b. What percent of the trucks logged more than 57,060 but less than 58,280 miles?
c. What percent of the Fords traveled 62,000 miles or less during the year?
d. Is it reasonable to conclude that any of the trucks were driven more than 70,000 miles?
Basically, in a case like this, you want to use the fact that we have normal distribution and a mean and standard deviation to calculate a z-score, or standard normal value (page 229 of your text) for the questions in ...
Using sample mean and standard deviation to make probablistic assessments of a data set. Practical application of z-score when assuming normal distribution of the population.