Question

Battery manufacturers compete on the basis of the amount of time their products last in cameras and toys. A manufacturer of alkaline batteries has observed that its batteries last for an average of 32 hours when used in a toy racing car. The amount of time is normally distributed with a standard deviation of 4.5 hours. What is the probability that the battery lasts fewer than 30 hours?

Answer 1

0.3284 or 32.84%

Explanation:

Here we want to find the area under the Normal curve with mean 32 and standard deviation 4.5 to the left of 30.

This can be found in Excel with the formula

NORMDIST(30,32,4.5,1)

and in OpenOffice Calc with

NORMDIST(30;32;4.5;1)

This area is

0.3284

(See picture)

so the probability that the battery lasts fewer than 30 hours is

0.3284 or 32.84%