# Suppose 6

Suppose the life span of a revolutionary light bulb is normally distributed with a mean life span of 70 thousand hours and a standard deviation of 3 thousand hours. If a light bulb is chosen at random:

a) what is the probability the life span will be within 5 thousand hours of the mean;

b) what must its lifetime be if it is to be categorized in the tallest 5%?

a) what is the probability the life span will be within 5 thousand hours of the mean;

b) what must its lifetime be if it is to be categorized in the tallest 5%?

### Correct answer:

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