Question

The life span of a battrery is normally distributed with a mean of 2100 hours and a standard deviation of 20 hours. What percent of batteries have a life span more than 2125 hours? would it be unusual for a battery to have a life span that is more than 2125 hours?

Answer 1

Use the chart to find how much of the normal distribution is above z = 1.25. I think it happens often enough that you wouldn't think it to be too unusual.

Answer 2

By my reckoning, it happens a little more than 10% of the time.

Answer 3

I'm a little older, so I use the chart from a book; you may have a way to do it on a calculator or computer.

Answer 4

LOL so am I. I used a chart.

Answer 5

Do math every day.