from Amazon
Friday, November 11, 2011
Performance in year after PED use
David Wade does some good work, but also some questionable conclusions. First the good stuff: for nonpitchers in the last year of PED use, they had 0.42 WAR higher than in the year after. But, as you guys know, there’s a natural 0.5 wins drop in WAR year-to-year due strictly to age-related reasons. So, if anything, he shows it’s no big deal.
But he throws out this doozy:
From ‘09 to ‘10, the average hitter who qualified for the batting title saw his WAR improve by nearly 1.8 wins, a change far larger than the 0.4 win improvement that our average user showed in the year he was using.
I don’t know how many times we have to deal with this selection bias issue, but here we go again. It seems to me that he started with the list of players who had at least 500 PA in 2010, and then looked to see how they did in 2009. He can’t do that.