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.

Driver	Manufacturer A	Manufacturer B
1	32	28
2	27	22
3	26	27
4	26	24
5	25	24
6	29	25
7	31	28
8	25	27

Refer to Exhibit 10-9. The mean for the differences is

	a) 0.50
	b) 1.5
	c) 2.0
	d) 2.5

Answer 1

The data for differences is:

4, 5, -1, 2, 1, 4, 3, -2

Hence,

Mean of differences = (4 + 5 - 1 + 2 + 1 + 4 + 3 - 2)/8 = 2.0

Option C is correct.