The mean life of pair of shoes is 40 months with a standard deviation of 8 months.If the life of the shoes is normally distributed,how many pairs of shoes out of one million will need replacement before 36 months?
A)500,000
B)808,500
C)191,500
D)308,500
E)705,100

Question

Quizplus · Accepted Answer

The z-score for 36 months is (36 - 40) / 8 = -0.5. The area under the normal curve to the left of -0.5 is 0.3085. Therefore, 308,500 pairs of shoes out of one million will need replacement before 36 months.

The Mean Life of Pair of Shoes Is 40 Months