SOLUTION: The mean life of electric bulbs is 2000 hrs. The standard deviation is 60 hrs. What is the probability of the bulbs burning for more than 2100 hrs and less than 1900 hrs?

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Question 947554: The mean life of electric bulbs is 2000 hrs. The standard deviation is 60 hrs.
What is the probability of the bulbs burning for more than 2100 hrs and less than 1900 hrs?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The mean life of electric bulbs is 2000 hrs. The standard deviation is 60 hrs.
What is the probability of the bulbs burning for more than 2100 hrs and less than 1900 hrs?
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z(2100) = (2100-2000)/60 = 100/60 = 5/3
z(1900) = (1900-2000)/60 = -5/3
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P(1900<= x <=2100) = P(-5/3< z < 5/3) = 0.9044
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Cheers,
Stan H.
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