Question

The amount of time a certain brand of light bulb lasts is normally distributed with a

mean of 800 hours and a standard deviation of 50 hours. what is the probability that
a randomly chosen light bulb will last between 780 hours and 810 hours, to the
nearest thousandth?

Answer 1

23.47 % ( or .2347)

Explanation:

780 is 20/50 = .4 for z score - .4

810 is 10/50 = .2 z-score = .2

Use z-score table .5793 - .3446 = .2347 23.47%