Normalize each male runner's time by the fastest time for the runner of the same age. To do this, find the fastest runner for each year of age from 20 to 80. The tapply () function may be helpful here. Smooth these times using loess (), and find the smoothed time using predict (). Use these smoothed times to normalize each run time. Use density plots, quantile-quantile plots, and summary statistics to compare the distribution of the age-normalized times for the runners in 1999 and 2012. What do you find? Repeat the process for the women. Compare the women in 1999 to the women in 2012 and to the men in 1999 and 2012.