Question

The life expectancy of a typical lightbulb is normally distributed with a mean of 2,000 hours and a standard deviation of 27 hours. What is the probability that a lightbulb will last between 1,975 and 2,050 hours? all I know about this question is that I have to use a z-score

Answer 1

@dan815

Answer 2

@Preetha

Answer 3

Here, we want to know the probability that bulb falls between and 1975 and 2050. The "trick" to solving this problem is to realize the following:

P( 1975 < X < 2050 ) = P( X < 2050 ) - P( X < 1975 )