The tread life of a particular brand of tire is a random variable best described by a normal distribution with a mean of 60,000 miles and a standard deviation of 1700 miles. What is the probability a certain tire of this brand will last between 56,430 miles and 56,940 miles?
A) .0180
B) .9813
C) .4920
D) .4649

Question

Quizplus · Accepted Answer

The probability is found by standardizing the values and using a normal distribution table. The standardized values are (56,430 - 60,000) / 1700 = -2.1 and (56,940 - 60,000) / 1700 = -1.8. The probability between these two values is 0.0180.

The Tread Life of a Particular Brand of Tire Is