SOLUTION: A new fluorescent light to replace incandescent bulbs has come on the market. The box says life of 8,000 hours with a standard deviation of 750 hours. A random sample of 50 light b

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Question 586714: A new fluorescent light to replace incandescent bulbs has come on the market. The box says life of 8,000 hours with a standard deviation of 750 hours. A random sample of 50 light bulbs is taken. Let Xbar be the mean of the sample.
A. What is the probability that Xbar is >or equal to 7900?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A new fluorescent light to replace incandescent bulbs has come on the market. The box says life of 8,000 hours with a standard deviation of 750 hours. A random sample of 50 light bulbs is taken. Let Xbar be the mean of the sample.
A. What is the probability that Xbar is >or equal to 7900?
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z(7900) = (7900-8000)/[750/sqrt(50)] = -0.9428
P(x-bar >= 7900) = P(z>-0.9428) = 0.8271
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Cheers,
Stan H.