SOLUTION: suppose that the lifetimes of light bulbs are approximately normally distributed, with a mean of 57 hours and a standard deviation 3.3 of hours. with this information, answer
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Question 1169990: suppose that the lifetimes of light bulbs are approximately normally distributed, with a mean of 57 hours and a standard deviation 3.3 of hours. with this information, answer the following questions.
(a) what proportion of light bulbs will last more than 60 hours?
(b) what proportion of light bulbs will last 51 hours or less?
(c) what proportion of light bulbs will last between 57 and 61 hours?
(d) what is the probability that a randomly selected light bulb lasts less than 45 hours? Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website! z=(x-mean)/sd
the first will be z > 3/3.3 or z > 0.909 . That probability is 0.1817
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the second will be z < -6/3.3 and that probability is 0.0345
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the third is 0.3873. Calculator 2ndVARS 2 normalcdf(57,61,57,3.3)ENTER
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the last is z < -12/3.3 and probability is 0.0001
