Two major automobile manufacturers have produced compact cars with engines of the same size.We are interested in determining whether or not there is a significant difference in the mean MPG (miles per gallon) when testing for the fuel efficiency of these two brands of automobiles.A random sample of eight cars from each manufacturer is selected, and eight drivers are selected to drive each automobile for a specified distance.The following data (in miles per gallon) show the results of the test.Assume the population of differences is normally distributed. The mean of the differences is

A) .5.
B) 1.5.
C) 2.0.
D) 2.5.

Question

Two major automobile manufacturers have produced compact cars with engines of the same size.We are interested in determining whether or not there is a significant difference in the mean MPG (miles per gallon) when testing for the fuel efficiency of these two brands of automobiles.A random sample of eight cars from each manufacturer is selected, and eight drivers are selected to drive each automobile for a specified distance.The following data (in miles per gallon) show the results of the test.Assume the population of differences is normally distributed.

The mean of the differences is

A) .5.
B) 1.5.
C) 2.0.
D) 2.5.

Stephen Lindsey · Accepted Answer

Final Answer : C, Explanation :  The mean of the differences can be calculated by taking the difference between each pair of MPG measurements and finding the average of those differences. It comes out to be (20-18)+(22-21)+(21-20)+(25-23)+(22-20)+(24-23)+(24-22)+(26-24)/8 = 2.0. Therefore, the answer is C.

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