Question 1010455: The life expectancy of a typical lightbulb is normally distributed with a mean of 1,975 hours and a standard deviation of 25 hours. What is the probability that a lightbulb will last between 1,950 and 2,050 hours?
0.84
0.77
0.82
0.89
Please show how you got the answer so I can learn please.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! The life expectancy of a typical lightbulb is normally distributed with a mean of 1,975 hours and a standard deviation of 25 hours. What is the probability that a lightbulb will last between 1,950 and 2,050 hours?
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z(1950) = (1950-1975)/25 = -1
z(2050) = (2050-1975)/25 = 75/25 = 3
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P(1950< x <2050) = P(-1< z <3) = 0.84
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Cheers,
Stan H.
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0.84
0.77
0.82
0.89
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