Atmospheric pressure and the boiling point of water
estimate of pressure = 116.59 − 1.4165 x + 0.004752 x2
estimate of ln (pressure) = −0.9518 + 0.02052 x
These two equations are the least squares fits of a quadratic model and a model using a transformed response. Use the pop-up menu to display them on the scatterplot and note that they fit the data equally well.
Use the slider to expand the scale and see the implications of both models. Explain that we have no idea of what the shape of the model should be beyond the data — it could be different from either of these models.
Avoid extrapolation.
In the mid 19th century, J. D. Forbes measured the boiling point of water (degrees Fahrenheit) and barometric pressure (inches of mercury) at 17 locations in the Alps and in Scotland.