OPS+ is OPS adjusted by league and (gasp!) park factors. Please dear god stop pretending to be a stats guy. Wow, I laughed so hard I teared up a bit. Thanks for bumping this thread. I can't believe I haven't seen this. Being the resident stat guy, I think this is a good opportunity for me rant on park factors. Everyone seems to misinterpret them. It doesn't matter how statistically inclined you are. It's not because people are dumb (they're not). It's because they misinterpret the meaning of them. OPS+ is NOT a measure of talent. It never was intended to be. EqA is NOT a measure of talent. It was never meant to be. GPA is NOT a measure of talent. It was never meant to be. DRA is NOT a measure of talent. It was never meant to be. wOBA is NOT a measure of talent. It was never meant to be. All of these major statistics measure production. The difference between the analysis of talent and production is the difference between the future and past. A players output is not a martingale, if it were the two would be the same. Production has an intrinsic concept of being compared to something more than talent would. Statistics measuring production always boil down being compared to one of two things: average level players and replacement level players. Since they want to measure a players production rate to the rate of an average (replacement) level player. The analysis is relatively simple. What would a league average (replacement) level player due if he was given the playing time of our player? Just the league average run effect. HR, BB, 2B, 3B, K, etc PFs are irrelevant. We don't care about how the park plays on a micro level. The only thing that matters is what happens to an average player on a macro rate. However, when trying to make some educated guess on a players true talent level, a lot more work is needed to be done. This is why things like EqA, wOBA, etc suck ass at this. Parks effects on an individuals stat line are much more of a micro level than a macro effect. To make changes like this we need a large spectrum of park factors which eventually is more of a dynamical system than any kind of park factor we're used to seeing. In order to make guess worth crap on a true translation out of a park for a player we need to a stat line completely. We can't just make a simple change. I don't have the answer to this. That's the million dollar question. No one has a system that does this well. The best may be the DTs on BP, but they're still useless. Quite frankly, none of the people interested in these sorts of things have the mathematical modeling and probability background in order to derive something better. Let's be honest, most people working in sabermetrics really don't have more than an undergraduate college background in stat or whatever. It's pretty damn obvious reading their "research". That's not to say they're dumb or wrong or anything. It's just that if someone with relevant background got interested, things would get real interesting. But anyways, about PFs and OPS+. It measures production. It doesn't measure talent. Parks affect each player differently, we need systems that adjust for that. /rant.