Additives-R-Us has developed an additive to improve fuel effi ciency for trucks that pull very heavy loads. They tested the additive by randomly selecting 18 trucks and dividing them into 9 pairs. In each pair, both trucks hauled the same type of load over the same roadway, but only one truck used fuel with the new additive. Different pairs followed different routes and carried different loads. The resulting fuel effi ciencies (in miles per gallon) are given below. Do the data indicate, at α = 0.01, that trucks using fuel with the additive achieved signifi cantly better fuel effi ciency than trucks using regular fuel?
- Find the mean change in earnings per share between 1991 and 1992.
- Find the standard deviation of the change and the standard error of the mean.
- Were average earnings per share different in 1991 and 1992? Test at α = 0.02.
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