by PuckStopsHere on 06/17/10 at 12:49 PM ET
A few days ago, I listed the top 20 adjusted +/- ratings calculated as a counting stat. I went on to write about Jeff Schultz of the Washington Capitals leading the league and the interpretation of that fact. I was asked the intelligent question by a commenter called GoPens about why these results show some discrepancies with what he had seen using +/- as a rate stat. The rate stat adjustment looks at +/- calculated per minute of play, while the counting stat adjustment looks at the total numbers accomplished in the entire season. Both are useful. The rate stat adjustment is better at finding seldom used players who are doing quite well and the counting stat adjustment is better at finding the top performances in the league. It is essentially the difference between goals scored and goals per game. I would argue that the counting stat is often more useful, in the same way that it is more useful to have a fifty goal scorer on your team than a guy who scored at a 50 goal pace but only played 10 games.
I think it is useful to look at the top adjusted +/- ratings when calculated as a rate stat and compare with the counting stat list. So here is the rate stat list (this is calculated from behind the net and only includes players with at least 50 games played in the 2009/10 regular season):
Rank in Counting Top 20
The top players appear on both lists but with their order shuffled. The bottom half of these lists tend to deviate from one another more than they do at the top. The rate stat list will tend to have more players who did not play very much and thus did not accumulate big enough counting numbers. As a result it is harder for a defenceman to make this list. There are six defencemen in the top 20 rate adjusted +/- list (Fistric, Schultz, Smid, Franson, Ehrhoff and Green) and nine on the counting list (Schultz, Fistric, Ehrhoff, Green, Rafalski, Pronger, Lidstrom, Chara and Carle). Some significant all star defencemen made the counting list and not the rate list. The only defencemen on the rate list but not the counting list are Ladislav Smid of the Oilers who was limited to 51 games played this season and Cody Fransen of the Predators who was limited to 61 games.
As for the exact order of the players on this list, Mark Fistric is a bit of a surprising number one. He did very well on the counting list (number three) as well. I promised a future post about Mark Fistric on the counting list post and it is even more clear that it is needed after seeing him leading this list. That will come soon.
Plus minus can be adjusted to attempt to remove team effects in multiple ways. The most common two methods treat it as a counting stat and as a rate stat respectively. Both are looking for slightly different things and it is expected that they should produce different (but similar) results. They are useful methods to find players who performed well in their roles in a given season. The rate stat adjustment, shown today, is better able to locate players who had good underlying numbers but limited playing time, while the counting stat adjustment is better able to find players who had strong seasons.
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