Regression of fuel consumption with respect to car weight in the xauto data
In the dataset uploaded using the SSC package xauto, we fitted a linear regression model of fuel consumption (in nipperkins per mile) with respect to car weight (in US tons), separately for the 2 car model origin groups (non-US models and US models). In each regression model, the regression slope was a weight effect on fuel consumption (expressed in nipperkins per additional ton-mile), and the intercept was a mean fuel consumption (expressed in nipperkins per mile) for a fantasy car with zero weight.
Table 1. Regression of fuel consumption with respect to weight (long version using insingap)
| Parameter | Estimate | (95% | CI) | P |
|---|
| Non-US (N=22): |
| Weight (US tons) | 11.059 | (8.130, | 13.987) | 1.5x10-7 |
| Constant | -1.764 | (-5.382, | 1.853) | .32 |
| US (N=52): |
| Weight (US tons) | 7.885 | (6.484, | 9.286) | 2.2x10-15 |
| Constant | 0.537 | (-1.549, | 2.622) | .61 |
Table 2. Regression of fuel consumption with respect to weight (wide version using xrewide)
| | Non-US (N=22): | | | | US (N=52): | | | |
|---|
| Parameter | Estimate | (95% | CI) | P | Estimate | (95% | CI) | P |
|---|
| Weight (US tons) | 11.059 | (8.130, | 13.987) | 1.5x10-7 | 7.885 | (6.484, | 9.286) | 2.2x10-15 |
| Constant | -1.764 | (-5.382, | 1.853) | .32 | 0.537 | (-1.549, | 2.622) | .61 |