STAT-uration - Vol One: The Plus/Minus

[count55]

With the advent of easy access to computers, fantasy sports, and the internet, there has been an explosion in not only the amount of statistics available, but the sheer number of metrics used to measure the performance of athletes and teams across all sports. It's even reached the point where statistical modeling is used not just as a tool of sports management, but in some cases, as the primary decision-making tool/driver of professional franchises.

I thought it'd be interesting to open a discussion about the value of this turn of events. However, rather than starting an esoteric discussion on the broad nature of the subject, I thought we'd go through different metrics. The idea being that we understand what the metric is, and how it is used. Then we can discuss how valid we think it is, how it should be used, whether it's being used correctly, and how relevant it is to the way we think.

Considering that this is a forum where disagreements arise regularly, maybe it would help for us to come to some conclusions and understanding about the stats we may or should (or shouldn't) use to support our positions.

The first subject will be "The Plus/Minus Rating".

The Plus/Minus rating is a simple calculation of point differential a team has when a certain player is on the floor. If John Smith enters the game with the score tied, then his team is up 6 points when he leaves the game, he gets a +6 rating.

The implication is that this is an indicator of how his team performs when he is in the game

This jumps out at me because of this information:



Is Danny Granger our worst player? (Yeah, that's what I thought.)

So...what does this mean? How do we use this? How do we factor teammates into this?

What do we do/think of the Plus/Minus rating?

[APerna]

I hate the plus-minus in basketball. I think it's a very effective tool in hockey, but doesn't transfer off the ice. Look at the top two?

Stephen Graham only has that high of a rating because he plays so rarely and David Harrison's value is probably that high because he fouls so much that the game and scoring gets slowed down in his few minutes per game.

Also, I think eighty percent of basketball people would say that Danny is probably our best all-around player (with promise included). So how the heck does a (3.26) rating per game do him justice?

I'm a fan of numbers, but (+/-) don't hold value if you ask me.

[mizzoupacers]

I think that plus/minus is fairly worthless in and of itself.

Basketball is a team game. One guy out of ten, that's a pretty limited influence. Put LeBron on the Timberwolves, and he would probably have a negative value according to plus/minus, because he would be on the court all the time, and most of that time the T Wolves would be losing.

It also does not take into account playing situations, or amount of time played. Does a guy typically play against other teams' starting units, or against their bench players? Is he playing in close games, or only in garbage time?

If you want to know who is valuable to your team, minutes played is a far more valuable measure. I'd argue that more often than not, minutes played correlates much more strongly to true value than does plus/minus. The guys who play the most, play the most because they are the most indispensable. Unless your team is coached by Isiah Thomas.

[granger05]

While we're talking about stats, I have to ask this. I get my box scores from Yahoo sports typically and they've added another category this year. In addition to all the usual, A, S, B, TO, etc... they now have a final category after Blocks which is labelled "BA." What the hell is a BA? There's no legend anywhere on the page. I'm a bit embarassed that I can't figure it out. Last night against Detroit, here were the BAs collected.

Williams: 4
Granger: 2
Dunleavy, Daniels, Murphy, Owens, Diogu: 1

On the subject of +/-, we're not a good team so we get outscored a lot. Danny plays the most so he gets the brunt of that. I don't think it's very meaningful.

[APerna]

BA is the shots they have blocked....I believe....so the stats should reverse for each team...so last night's box score would say that the Pistons blocked 7 shots...(4+2+1)

[count55]

BA's, I believe are "Blocks Against"... You will see that the BA matches the BS on the other team, and vice versa.

Of course, nobody matches the BS when Bill Walton is doing the game...

ba-dump-bump....

Take my wife...please.

[joew8302]

I like the plus/minus statistic, but not for individual player evaluations. I think it can be a useful tool to decide what combinations work well and what combos don't. Like you guys have said though, you have to trust your eyes and interpret the plus/minus for what it is, it shouldn't ever be a crutch.

[harding156]

I hate the plus-minus in basketball. I think it's a very effective tool in hockey, but doesn't transfer off the ice. Look at the top two?

The +/- system is definitely more effective in hockey, but I'm still not a fan of it. If you share a lot of ice time with someone like Joe Thornton or Sidney Crosby, it's going to improve your +/- rating regardless if you're doing anything or not. Having a very good goalie will inflate your +/- rating as well. It works the other way too. If you're surrounded by idiots, or just have a bad goalie, your +/- rating will be lower than it should be.

But, the worst stat in hockey has to go to GWG(game winning goals). Let's say a player scores a goal in the first couple minutes of a game, if his team holds the lead for the rest of the game he gets the GWG. It doesn't matter if they win 6-0, he still gets it. It's kind of like giving a starting pitcher a save if he pitches a complete game and wins.

As for +/- in basketball, it just doesn't work at all. One of the main reasons I think it's worthless is there is just too much garbage time. Too many games end with the last few minutes being layup drills and 3 point contests. And don't forget the teams that play the foul game well after they actually have a chance to win.

The only thing it's good for in basketball is you can look at the +/- for a team's entire roster, like the Pacers in count's post, and see if the team is any good or not. Then again, you could also just look at the standings.

[notque]

I'm the stat guy that always gets busted here for using stats, so it's nice someone else brought this up.

Plus/Minus doesn't tell you anything about a particular player used as you are doing now.

Plus/Minus can be used as a tool to determine which players work well together, and which players don't.

That's about it. It's meaningless without it's context.

[Boneman2]

In defense of the +/- system, it is much more effective if you apply it to a winning team. Then it may point out trends in the lineup.

I would guess Wade or Al Jefferson don't fair too well in this system either.

[Grang33r]

I love the plus-minus in basketball and if you all remember few years ago, maybe 2002 or so, Conrad Brunner of Pacers.com always had a updated +/- chart for the Pacers. At the time, it wasn't a official NBA stat and almost no team used it or cared for it. Brunner wrote an article on pacers.com once stating that many teams have talked to him about the stat and the formula. Brunner said it was a very important stat and he said those who have researched his work, agreed. Now, this is the first year the +/- is an official stat by the league (meaning NBA now pays somebody to actually keep up with the stats).