Kelso Motor Parts produces a car battery with a useful life that has a normal distribution.Average life is 40,000 miles, with a standard deviation of 1500 miles.What proportion of the batteries will have a useful life of less than 39,000 miles?
A).2514
B).1056
C).2669
D).1673
E).2014

Question

Quizplus · Accepted Answer

The z-score for a useful life of 39,000 miles is (39,000 - 40,000) / 1500 = -0.67. The proportion of the batteries with a useful life of less than 39,000 miles is the area under the normal distribution to the left of -0.67, which is 0.2514.

Kelso Motor Parts Produces a Car Battery with a Useful