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. What percentage of tires will have a life of 35,000 to 45,000 miles?
A) 31.73%
B) 68.27%
C) 50%
D) 95%

Question

Quizplus · Accepted Answer

This range (35,000 to 45,000 miles) is within one standard deviation (±5,000 miles) from the mean (40,000 miles) in a normal distribution. According to the empirical rule (68-95-99.7 rule), approximately 68% of the data falls within one standard deviation of the mean in a normal distribution.

The Life Expectancy of a Particular Brand of Tire Is