• Story Name: Passenger Car Mileage
  • Story Topics: Automotive, Engineering, Consumer,
  • Datafile Name: Passenger Car Mileage
  • Methods: Regression, Transformation, Polynomial Regression,
  • Abstract:

    Variation in gasoline mileage among makes and models of automobiles is influenced substantially by the weight and horsepower of the vehicles. When miles per gallon and horsepower are transformed to logarithms, the linearity of the regression is improved. A negative second order term is required to fit the logarathmic mileage to weight relation. If the logged variables are standardized, the coefficients of the first order terms indicate the standard units change in log mileage per one standard unit change in the predictor variable at the (logarithmic) mean. This change is constant in the case of mileage to horsepower, but not for mileage to weight. The coefficient of the second order weight term indicates the change in standardized slope associ- ated with a one standard deviation increase in the logarithm of weight.

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