What does plus-minus mean in basketball box score?

Answer 1

The +/- stat is tied to team performance during the time that that particular player is on the court. The games official scorer records the differential in terms of gain (plus) or loss (minus).

By way of example, if David Lee enters the game with the score tied at 80 to 80, and leaves with his team ahead by 3, he gets a plus 3. Conversely, if he enters with his team ahead by 13, and leaves with a 3 point lead, he gets a minus-10.

These numbers are added up throughout the game until at the end you have your final +/- for each player that you see in the box score.

More to the point, as the NBA explains:

The +/- stat shows the power of teamwork. It's a way of showing the best-engineered/best combination of players on the court. The +/- stat is a statistic that looks at the point differential when players are both in and out of the game, to see how the team performs with various combinations. The +/- stat can look at a variety of combinations including the best two player, three player and even five player combinations for each game.

For example, through their exit in the 2011 conference semifinals, the Boston Celtics has the best cumulative 9-game composite +/- of +64 (9 games) with the combination of Kevin Garnett, Ray Allen, Jermaine O'Neal, Paul Pierce and Rajan Rondo, ahead of the Memphis Grizzlies (prior to the game of 13 May 2011), who have a cumulative +/- of +48 with the combination of Shane Battier, Zach Randolph, Mike Conley, Marc Gasol and OJ Mayo.