Question

The life span of a battery is normally distributed, with a mean of 2000 hours and a standard deviation of 50 hours. A) What percent of batteries have a life span that is more than 2080 hours? B) Would it be unusual for a battery to have a life span that is more than 2080 hours? [Explain your reasoning.]

What percent of batteries have a life span that is more than 2080 ​hours?

Approximately ___% of batteries have a life span that is more than 2080 hours. ​(Round to two decimal places as​ needed.)

Answer 1

a) P(X > 2080)

= P(z > (2080 - 2000)/50)

= P(z > 1.6)

= 0.0548

Approximately 5.48 % of batteries have a life span that is more than 2080 hours.

b) This is not unusual because its probability is greater than 0.05.