SOLUTION: solve the problem suppose that replacement times of washing machines are normally distributed with a mean of 9.3 years and a standard deviation of 1.1 years. Find the probability t

Question 216036: solve the problem suppose that replacement times of washing machines are normally distributed with a mean of 9.3 years and a standard deviation of 1.1 years. Find the probability that 70 randomly selected washing machines will have a mean replacement times less than 9.1 years.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
suppose that replacement times of washing machines are normally distributed with a mean of 9.3 years and a standard deviation of 1.1 years. Find the probability that 70 randomly selected washing machines will have a mean replacement times less than 9.1 years.
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The sample standard deviation is 1.1/sqrt(70) = 0.1315
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Find the z-value of 9.1
z(9.1) = (9.1-9.3)/0.1315 = -1.5209...
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P(x<9.1) = P(z< -1.5209) = 0.06414...
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Cheers,
Stan H.
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