SOLUTION: A company installs 5,000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, distribution approximated by a normal curve. Find the approximate nu

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Question 929919: A company installs 5,000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, distribution approximated by a normal curve. Find the approximate number of bulbs that can be expected to last more than 400 hours?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
mean = 500hr, sd = 100hr, z+=+blue%28x+-+500%29%2Fblue%28100%29
p(x > 400) = P( z > -100/100) = normalcdf( -1, 100) = .84
.84*5000 = 4200 bulbs can be expected to last more than 400 hours