TomTom, the producer of GPS devices, reported that the fastest drivers in the nation are in Mississippi. In Mississippi, interstate drivers average 70.1 miles per hour. Assume that the speed of cars traveling on Mississippi’s interstates follows the normal distribution with a standard deviation of 7.2 miles per hour.
a. What is the probability that a randomly selected car on a Mississippi interstate is traveling
1. faster than 65 miles per hour?
2. slower than 72 miles per hour?
3. between 60 and 66 miles per hour?
4. between 78 and 85 miles per hour?
b. Confirm the answers to part a with Excel or PHStat.
c. What average speed should I drive if I want to travel faster than 70% of the cars on the interstate?