Computers in some vehicles calculate various quantities related to performance. One of these is the fuel efficiency, or gas mileage, usually expressed as miles per gallon (mpg). For one vehicle equipped in this way, the mpg were recorded each time the gas tank was filled, and the computer was then reset. In addition to the computer calculating mpg, the driver also recorded the mpg by dividing the miles driven by the amount of gallons at fill-up. The driver wants to determine if these calculations are different.
Fill-up 1 2 3 4 5 6 7 8 9 10
Computer 41.5 50.5 36.6 37.3 34.5 45.0 47.7 43.0 47.4 42.2
Driver 36.5 44.2 37.2 35.6 30.5 40.5 40.0 41.0 42.8 39.2
Fill-up 11 12 13 14 15 16 17 18 19 20
Computer 43.3 44.5 48.1 46.1 46.7 39.5 37.6 43.3 44.2 43.3
Driver 38.8 44.5 45.4 45.3 45.7 34.2 35.2 39.8 44.9 47.5
Find t, degrees of freedom, and P-value