The following question comes from Forecasting: Principles and Practice 3d Edition : Chapter 7.10 Exc2 (Choose 1 men's event)

Data setolympic_runningcontains the winning times (in seconds) in each Olympic Games sprint, middle-distance and long-distance track events from 1896 to 2016.

1. Plot the winning time against the year for each event. Describe the main features of the plot.
2. Fit a regression line to the data for each event. Obviously the winning times have been decreasing, but at whataveragerate per year?
3. Plot the residuals against the year. What does this indicate about the suitability of the fitted lines?
4. Predict the winning time for each race in the 2020 Olympics. Give a prediction interval for your forecasts. What assumptions have you made in these calculations?