Dec 17, 2009
According to this line of argument, since steroids should improve driving distances, and since driving distance determines overall performance, the fact that his average driving distance "remained almost constant throughout the years" proved that he did not dope.
Now, I have no idea if he dopes or not. But this particular argument is full of holes. In the modern era, steroids are used not just for enhancing brute strength but also shortening recovery times, prolonging training, etc. Also, it holds only if overall performance is heavily affected by driving distance.
The bar chart has multiple problems:
Why were those three years chosen? The following line chart that plots all the data may give us a clue:
The choice of 2001 and 2009 means we missed the peak of his driving distance performance. Looking at the standardized units, we see that at its peak, the driving distance was about 2.6 times the standard deviation above his career average (the zero line using the scale on the right).
The difference between 1997 and the peak was about 20, which looked large compared to the standard deviation of 6 over this entire period. Establishing a reference point is very important to interpreting any observed difference.
This is one of the few occasions where double axes can be recommended. The two axes in fact plot the same data, only reflecting a difference in scale.
Reference: "Three reasons to believe he's totally clean", Metro USA, Dec 16 2009.
If you select your data carefully, you can let yourself believe anything.
Posted by: Jon Peltier | Dec 17, 2009 at 10:57 PM