FanPost

On the randomness of plus/minus


I am not a fan of using a player's plus/minus as a barometer of their play on the ice. However, many coaches, players and fans disagree -- and that is OK, but the metric is far from perfect.

I decided to set up a simulation to show just how inconsistent the metric can be. I created a player who has absolutely no impact on the game. For both his team and his opponent, there is an 8 percent chance of scoring a goal on a shot during even-strength. I am assuming that this player is on the ice for 11 even-strength minutes per game and will be on the ice for six shots for and six against*. I ran the simulation for 1000 82-game seasons, and as you can see, the metric is full of statistical noise.

Plusminussim_medium

If the plus-minus statistic were truly fair there would be nothing but zeroes on the chart because like I said, this player has absolutely no statistical impact on the game. Instead, this player is just as likely to be plus-10 or better in a season as he is minus-10 or worse.

Sure, there is noise in any statistic, but this chart shows that the amount of noise in plus-minus is unacceptable. Imagine the narratives that would be written about this same player: how he was too slow, not scoring enough, etc. Some may even feel that the player should be a healthy scratch, when in reality it is simply randomness creating the numbers.

* All bits and bytes appearing in this work are fictitious. Any resemblance to real persons, living or dead, that may or may not rhyme with Pike Panoobell is purely intentional.

If this FanPost is written by someone other than one of the blog's editors, the opinions expressed in it do not necessarily reflect those of this blog or SB Nation.

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