Exhibit 6-8
The life expectancy of a particular brand of tire is normally distributed with a mean of 40,000 and a standard deviation of 5,000 miles.
-Refer to Exhibit 6-8. What percentage of tires will have a life of 34,000 to 46,000 miles?
A)38.49%
B)76.98%
C)50%
D)88.49%

Question

Quizplus · Accepted Answer

We need to find the percentage of tires that will have a life of 34,000 to 46,000 miles. To do so, we standardize the values using the formula z = (x - mean) / standard deviation. For x = 34,000, z = (34,000 - 40,000) / 5,000 = -1.2. For x = 46,000, z = (46,000 - 40,000) / 5,000 = 1.2. Using a standard normal distribution table or calculator, we can find the area under the curve between z = -1.2 and z = 1.2, which is approximately 0.7698 or 76.98%. Therefore, 76.98% of tires will have a life of 34,000 to 46,000 miles.

Exhibit 6-8 The Life Expectancy of a Particular Brand of Tire Is