The table below shows estimated differences in fuel efficiency between foreign and domestic cars with and without adjustment for weight, using gallons per 100 miles as the outcome.
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(1) (2)
gphm gphm
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foreign -1.005** 0.622**
(-3.29) (3.11)
weight 0.00163***
(13.74)
_cons 5.318*** -0.0735
(31.92) (-0.18)
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N 74 74
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t statistics in parentheses
* p<0.05, ** p<0.01, *** p<0.001
We see that on average foreign cars are more economical, but if we adjust for weight they are less fuel efficient, using 0.6 gallons more instead of one gallon less per 100 miles.