Originally posted by madootra
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Truth is an "NHL" Official with a box of popcorn and an I-phone does his best to count the players #'s on the ice after each goal, 30% -40% of the time the tabulation is inaccurate, erroneous and misleading.
Shot-based metrics or Plus-Minus is really a team stat: measuring a player’s ability to some uncertain extent, but more so measuring the strength of everyone on ice– with a whole lot of random chance factored in too. I much prefer possession percentage instead of goal differential as in Corsi or Fenwick metrics.
Don't just take my word for it, I think Brian Burke perhaps said it best.
Just how “horse shit” is the NHL’s official plus-minus stat?
May 13, 2013. 8:25 pm
"A five-year study on team-based plus-minus numbers indicates it gives plus and minus marks to undeserving players at least one third of the time…
Long-time NHL executive Brian Burke has called the NHL’s official plus-minus number a “horse shit” stat.
The now venerable stat has long been the object of criticism from NHL players, coaches, general managers, reporters and, more recently, members of the advanced stats community.
One major and recurring criticism has been voiced since the stat became an official NHL number in 1967, namely that a good player who is surrounded by weak players will likely have a poor plus-minus number through little fault of his own, while a weaker player who is surrounded by strong players will have a good plus-minus number through little credit to himself.
Just how commonly does the official NHL plus -minus system award get it wrong, assigning false positives and false negatives?
In a five year study — compiled through game in, game out video analysis of every goal scored for and against the Edmonton Oilers from 2008 to 2013 — it’s apparent that on goals for, about 70 per cent of the plus marks are correctly assigned to players who make some contribution, major or minor, to the goal. But 30 per cent of the plus marks are awarded to players who make little or no contribution at all to the goal being scored.
On goals against, team derived plus-minus systems are even less fair and accurate. Half of the minus marks on goals against are handed out to players who make a major or minor mistake on the goal against, but half of the minus marks go to players who either had no impact on the play or were doing their job defensively but nonetheless are assigned a minus mark due to an erring teammate.
In the end, it’s safe to say that one third of the plus and minus marks handed out under the official plus-minus system are assigned to players who don’t deserve them, and the problem is greatest at the defensive end of the ice. This number of incorrect assignments is likely as high as 40 per cent of all plus-minus marks handed out."
http://blogs.edmontonjournal.com/201...us-minus-stat/
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