Question

Problem 10

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 70 mph. The tests showed that

the new tread pattern enables the cars to stop completely in an average distance of 120 feet with

a standard deviation of 7 feet and that the stopping distances are approximately normally

Problem 10

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 70 mph. The tests showed that the new tread pattern enables the cars to stop completely in an average distance of 120 feet with a standard deviation of 7 feet and that the stopping distances are approximately normally distributed.

(a) What is the 80th percentile?

(b) What is the probability that at least 4 out of 10 cars in the study will stop in a distance that is greater than the distance in part a?

(c) What is the probability that a randomly selected sample of 25 cars in the study will have a mean stopping distance of at least 130 feet?

Answer 1