A Researcher Wanted to Determine If Using an Octane Booster $X _ { 1 }$

question 91

Multiple Choice

A researcher wanted to determine if using an octane booster would increase gasoline mileage. A random sample of seven cars was selected; the cars were driven for two weeks without the booster and two weeks with the booster. Use the definitions of $X _ { 1 }$ and $X _ { 2 }$ as given in the table. Consequently, $D = X _ { 1 } - X _ { 2 }$ .


Determine the mean of the differences.

• A) -1.67
• B) -1.43
• C) 1.67
• D) 6.3

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