Question 642468: 1) a battery is found to have a mean life of 219 hours with a standard deviation of 70 hours. what is the probability that the battery will not last 100 hours??
2) students in the grade have an average height of 66 inches with a standard deviation of 3 inches. whats the probability that a student is less then 68 inches tall??
3) a bolt manufacturer makes bolts that have a mean diameter of of 1 cm with a standard deviation of 0.05. whats the probability that the diameter of the bolt will exceed 1.03 cm??
4) of popcorn kernels that pop successfully, the mean popping time for one batch is 4 min with a standard deviation of 1 min. what is the probability that a specific kernel will pop after 5 1/2 min
As you can see it is allot and its due tommorow morning so please help me solve these problems ASAP
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! 1) a battery is found to have a mean life of 219 hours with a standard deviation of 70 hours. what is the probability that the battery will not last 100 hours??
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z(100) = (100-219)/70 = -119/70 = -1.7
P(x < 100) = P(z < -1.7) = normalcdf(-100,-1.7) = 0.0446
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2) students in the grade have an average height of 66 inches with a standard deviation of 3 inches. whats the probability that a student is less then 68 inches tall??
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z(68) = (68-66)/3 = 2/3
P(x < 68) = P(z < 2/3) = normalcdf(-100,2/3) = 0.7475
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3) a bolt manufacturer makes bolts that have a mean diameter of of 1 cm with a standard deviation of 0.05. whats the probability that the diameter of the bolt will exceed 1.03 cm??
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z(1.03) = (1.03-1)/0.05 = 3/5
etc.
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4) of popcorn kernels that pop successfully, the mean popping time for one batch is 4 min with a standard deviation of 1 min. what is the probability that a specific kernel will pop after 5 1/2 min
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z(5 1/2) = (5 1/2 - 4)/1 = (1 1/2)/1 = 3/2
etc.
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Cheers,
Stan H.
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