Exhibit 10-9
Two major automobile manufacturers have produced compact cars with the same size engines. We are interested in determining whether or not there is a significant difference in the MPG (miles per gallon) of the 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 show the results of the test.
-Refer to Exhibit 10-9. The mean for the differences is
A)0.50
B)1.5
C)2.0
D)2.5

Question

Exhibit 10-9
Two major automobile manufacturers have produced compact cars with the same size engines. We are interested in determining whether or not there is a significant difference in the MPG (miles per gallon) of the 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 show the results of the test. 
-Refer to Exhibit 10-9. The mean for the differences is
A)0.50 
B)1.5 
C)2.0 
D)2.5

Quizplus · Accepted Answer

To find the mean for the differences, we need to calculate the difference between the MPG for each pair of cars and then take the average of those differences. For example, the first pair has a difference of 3 MPG (31 – 28) and the second pair has a difference of 1 MPG (29 – 28). The mean of these differences is (3+1+2+2+2+2+0+1)/8 = 2.0. Therefore, the best choice is C) 2.0.

Exhibit 10-9 Two Major Automobile Manufacturers Have Produced Compact Cars with the with the Same