SOLUTION: The average age of Amtrak passenger train cars is 19.4 years. If the distribution of ages is normal and 20% of the cars are older than 22.8 years, find the standard deviation.
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-> SOLUTION: The average age of Amtrak passenger train cars is 19.4 years. If the distribution of ages is normal and 20% of the cars are older than 22.8 years, find the standard deviation.
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Question 133640This question is from textbook Statistics
: The average age of Amtrak passenger train cars is 19.4 years. If the distribution of ages is normal and 20% of the cars are older than 22.8 years, find the standard deviation. This question is from textbook Statistics
You can put this solution on YOUR website! The average age of Amtrak passenger train cars is 19.4 years. If the distribution of ages is normal and 20% of the cars are older than 22.8 years, find the standard deviation.
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mu = 19.4
Find the z-value associated with upper 20%:
InvNorm(0.80) = 0.8416
Use z = (x-mu)/sigma to find sigma
0.8416 = (22.8-19.4)/sigma
sigma = (22.8-19.4)/0.8416
sigma = (3.4)/0.8416 = 4.0399
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Cheers,
Stan H.
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