Look once more at the data from Tour de France 2016. In Exercise 52, we looked at the whole history of the race, but now let’s consider just the modern era from 1967 on.

a) Make a scatterplot and find the regression of Avg Speed by Year only for years from 1967 to the present. Are the conditions for regression met?
b) The years 1999–2005 have been disqualified because of doping. How does this help explain the fact that 9 out of 10 residuals in the final 10 years are negative?
c) Would you extrapolate from this model to predict next year’s winning speed?

Data From Exercise 52

We met the Tour de France data set in  Chapter 1 (in Just Checking). One hundred years ago, the  fastest rider finished the course at an average speed of about 25.3 kph (around 15.8 mph). By the 21st century, winning  riders were averaging over 40 kph (nearly 25 mph).