Data set mens400 contains the winning times (in seconds) for the men’s 400 meters nal in each Olympic Games from 1896 to 2016. a. Plot the winning time against the year. Describe the main features of...

Data set mens400 contains the winning times (in seconds) for the men’s 400 meters nal in each Olympic Games from 1896 to 2016.

a. Plot the winning time against the year. Describe the main features of the plot.

b. Fit a regression line to the data. Obviously the winning times have been decreasing, but at what average rate per year?

c. Plot the residuals against the year. What does this indicate about the suitability of the tted line?

d. Predict the winning time for the men’s 400 meters nal in the 2020 Olympics. Give a prediction interval for your forecasts. What assumptions have you made in these calculations?