SOLUTION: A company installs light bulbs, each with an average life of 7000 hours, standard deviation of 796 hours, and distribution approximated by a normal curve. Find the percentage of th

Question 1180017: A company installs light bulbs, each with an average life of 7000 hours, standard deviation of 796 hours, and distribution approximated by a normal curve. Find the percentage of the bulbs that can be expected to last more than 8500hours? Round to the hundredth if necessary
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
mean is 7000 hours.
standard deviation is 796 hours.
z-score = (x - m) / x
x is the raw score = 8500
m is the mean = 7000
s is the standard deviation = 796 hours
z-score = (8500 - 7000) / 796 = 1.884422111.
area to the left of that z-score is .9702461149
area to the right = 1 minus that = .0297538851.
the percentage of light bulbs that can be expected to last more than 8400 is .0298 rounded to 4 decimal places = 2.98% rounded to 2 decimal places.
you can use the following calculator to get the same answer.
https://www.gigacalculator.com/calculators/z-score-calculator.php
let me know if you have any trouble getting the same results.

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