David Pinto has a good explanation of Type I and Type II error in the context of baseball’s new plan for steroid testing, while Jayson Stark has a pretty good Q and A on the agreement that nonetheless makes a rather dumb statement:

What’s amazing, in some ways, is that one positive steroid test actually carries a more serious penalty than a cocaine-possession conviction. One positive steroid test leads to an immediate suspension. It takes two cocaine convictions to get suspended.

Unless someone shows some evidence that doing coke or pot improves athletic performance, it seems to me that baseball is properly putting the emphasis on drugs that affect the integrity of the game; while it’s potentially embarrassing to the league to have a coke-head on the field, his presence doesn’t encourage any other player to do coke. Indeed, if coke and pot were legal substances, it’s likely the only ban on those substances in any sport would be on their use on the field because of public image issues, similar to the ban on tobacco use.