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??
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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.