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 2300 miles. What is the probability a particular tire of this brand will last longer than 57,700 miles?
A) .8413
B) .1587
C) .2266
D) .7266

Question

Quizplus · Accepted Answer

To find the probability that a tire lasts longer than 57,700 miles, we calculate the Z-score: Z = (57,700 - 60,000) / 2300 = -1. Using the standard normal distribution table, the probability of Z > -1 is 0.8413.

The Tread Life of a Particular Brand of Tire Is