A tire manufacturer designed a new tread pattern for its all-weather tires. Repeated tests were conducted on cars of approximately the same weight traveling at 60 miles per hour. The tests showed that the new tread pattern enables the cars to stop completely in an average distance of 125 feet with a standard deviation of 6.5 feet and that the stopping distances are approximately normally distributed.
-One car tested had a stopping distance of 112 feet. How many standard deviations was this car away from the mean stopping distance?
A) Thirteen standard deviations above the mean
B) Thirteen standard deviations below the mean
C) Two standard deviations above the mean
D) Two standard deviations below the mean

Question

Quizplus · Accepted Answer

The car's stopping distance of 112 feet is 13 feet below the mean of 125 feet. Dividing 13 feet by the standard deviation of 6.5 feet gives approximately 2 standard deviations below the mean.

A Tire Manufacturer Designed a New Tread Pattern for Its