Question 978190: The manufacturer of a new compact car claims the miles per gallon (mpg) for the gasoline consumption is mound-shaped and symmetric with a mean of 25.9 mpg and a standard deviation of 9.5 mpg. If 30 such cars are tested, what is the probability the average mpg achieved by these 30 cars will be greater than 28?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! The manufacturer of a new compact car claims the miles per gallon (mpg) for the gasoline consumption is mound-shaped and symmetric with a mean of 25.9 mpg and a standard deviation of 9.5 mpg.
If 30 such cars are tested, what is the probability the average mpg achieved by these 30 cars will be greater than 28?
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z(28) = (28-25.9)/(9.5/sqrt(30)) = 1.2108
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P(x-bar > 28) = P(z > 1.2108) = normalcdf(1.2108,100) = 0.1130
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Cheers,
Stan H.
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