Wednesday, June 11, 2014
Dear anti-plusminus-istas
Niklas Lidstrom has been on the ice for around 1600 even strength goals for and over 1100 even strength goals against. It is why his even-strength plus-minus is around +450. Does that mean nothing at all, as in zero? Is it just a coincidence that one of the greatest D in NHL history also happens to have one of the highest totals?
Now, we know the issues. Lidstrom has played on powerhouse teams (setting aside his own contributions to those powerhouse teams). That's why we ADJUST things. We adjust it, just as we'd adjust anything else, including plus-minus based on shots instead of plus-minus based on goals. Some players also get paired with other players for extended periods of time, making it doubly more difficult. Or matched with opposing players.
We adjust Larry Walker and Todd Helton in Coors. We adjust Sandy Koufax in Dodger Stadium in the 1960s. We adjust it by using our hockey-smarts and baseball-smarts. We take a look at the landscape, at the context, and then we adjust.
Yes, I know the other issue, that at the career level, we have 2000+ goal events, but at the seasonal level, we're down to only 100+ goal events. With shots, we have 1000+ shot events each year. That's sample size, and that means an uncertainty level. For BOTH metrics, those based on goals and those based on shots. We have a greater uncertainty level with metrics based on a smaller number of events.
However, you also have to accept that one goal tells us more than one shot. While 1000 shots might tell you more about a player than 100 goals, it's very possible that 2000 goal events will tell you more about a player than 20,000 shot events.
We have the same issue in baseball. Yes, a pitcher's FIP in one season will tell us more about the pitcher's talent than his actual runs allowed. And that's because his FIP (i.e., presumed performance based on K, BB, HB, HR events) has less noise than runs (which includes the timing of those events, plus the timing of non-HR hits, and however his teammates perform on the field, and who they throw out on the bases, etc). But at some point, his actual runs allowed will tell us more than his FIP about his talent.
That's how these things work. They ALL tell us something, at some point.
Only something like a pitcher's W/L record will tell you nothing, given that we know his runs allowed, his bullpen support, and his offensive support, game-by-game. That's because the W/L record is based on all that, and therefore, it contains no new information. None at all. (If you were missing any of those three pieces of information, and/or you were missing that information on a game-by-game basis, the pitcher W/L record WOULD contain new information.)
Goal differential contains information that shot differential does not. And shot differential contains information that goal differential does not. And therefore, BOTH have a certain amount of value. At a single-game level, shot differential will mean more. At a 15-year career level, goal differential will mean more. Somewhere in-between, the cross-over happens.
And whatever you do, adjust.
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