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There are 28 entries in the glossary.
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Term Definition
Adjusted Plus-Minus

Adjusted plus/minus is a way of rating players first developed by Wayne Winston and Jeff Sagarin in the form of their WINVAL system. For each player, it starts with the team’s average point differential for each possession when they are on the court. This gives a number showing how effective the player’s team was when they were in the game. The problem with using this to evaluate individual players is that it is biased in favor of players who play alongside great teammates (and players who play against weak opponents). Adjusted plus/minus uses regression analysis to control for these biases by controlling for the quality of the teammates a player played with and the opponents he played against.

To get more information about adjusted plus-minus calculation click here


Comments: The big advantage of adjusted plus/minus ratings are that they are the closest we can come to an "unbiased" measure of a player's effectiveness. So adjusted plus/minus ratings are almost unbiased but have a high variance.
 
Approximate Value

The metric which is an estimate of a player's value, making no fine distinctions, but, rather, distinguishing easily between very good seasons, average seasons, and poor seasons. There are two ways to calculate approximate value:


Credits=(Points)+(Rebounds)+(Assists)+(Steal)+(Blocks)-(Field Goals Missed)-(Free Throws Missed)-(Turnovers)
AV= (Credits(3/4) )/21

Alternative method shall be assigned according to the following rules shown here


Comments: Before the '73-74 season, steals, blocks, and turnovers weren't kept as official stats. In the credits formula, those stats are just omitted as they tend to cancel each other out to some degree when included anyway
 
Defensive Plus-Minus

A metric that measures the difference per 100 possessions in points allowed with a player on the court versus off the court. The accuracy of this measure varies dependent upon how often the player is on the floor and whom the player share it with. In most cases it provides a good indication of a player’s overall defensive value to his team.

 
Defensive Rating
Author: Dean Oliver

A metric which is invented by Dean Oliver. The premise of individual defense is that players force "defensive stops", preventing the other team from scoring.

An individual can do that by forcing a missed shot that then gets rebounded by his team, by getting a defensive rebound, by forcing a turnover, or by fouling a player who misses both foul shots, the second of which is then rebounded by the defense.

 
Defensive Stop

A defensive stop occurs when a player or team defense regains the ball without allowing the opponent a scoring possession.

Ways to get the "defensive stops" done:
1. Forcing a missed shot that then gets rebounded by his team,
2. Getting a defensive rebound,
3. Forcing a turnover,
4. Fouling a player who misses both foul shots, the second of which is then rebounded by the defense.

 
Diamond Rating
Author: Kevin Broom

A metric which is invented by Kevin Broom who devised a simple general formula that works with any per-minute statistics. Fomula subtracts the player's rating per game from his rating per 40 minutes to figure out how much his per game stats undervalue his potential contributions. He then subtracts league average from the player's per-40 minute rating and adds this amount to ensure the player is actually playing well in the minutes he does get.

Diamond Rating Formula=(Per Minute Rating)*40-(Per Minute Rating)*(Minutes Per Game)+[(Per Minute Rating)-(League's Per Minute Rating)]*40

 

 


Comments: The fewer minutes a player plays per game, and the better he does in those minutes, the better his Diamond Rating.Diamond Rating makes sense to eliminate players from consideration who are over 27, have more than five years experience, play more than 30 minutes per game or played less than 250 minutes total.
 
Game Score
Author: John Hollinger

A metric which is John Hollinger’s simple and linear version of the Player Efficiency Rating.

Game Score Formula =(Points)+0.4*(Field Goals Made)+0.7*(Offensive Rebounds)+0.3*(Defensive rebounds)+(Steals)+0.7*(Assists)+0.7*(Blocked Shots)- 0.7*(Field Goal Attempts)-0.4*(Free Throws Missed) - 0.4*(Personal Fouls)-(Turnovers)


Comments: Game Score does not make any adjustments like PER does for team pace. It simply adds and subtracts the box score statistics, according to the various weights Hollinger has chosen.
 
Individual Floor Percentage
Author: Dean Oliver

The metric that indicates the ratio of a player's scoring possessions by his total possessions. 

When a player ends his team's possession, it would be a possession charged to him. This is player's total possessions. When a player scored or assisted on a score, a scoring possession would be charged to him.

Individual Floor Percentage Formula=100*(Player's Scoring Possessions)/(Player's Total Possessions)

 
NBA Efficiency

A linear and basic metric which indicates players' efficiency.

NBA Efficiency Formula = (Points)+(Rebounds)+(Steals)+(Assists)+(Blocked Shots)-(Turnovers)-(Missed Shots)


Comments: NBA Efficiency does a nice job of explaining free agent salary. NBA Efficiency tells us about perceptions of performance. It just has some problems if our objective is to measure the impact a player has on wins.
 
Net Plus-Minus

A metric which is invented by Roland Beech based on team point differential while the player is on the court.

To get more information about Net Plus-Minus, click here 

 
Offensive Rating

A metric which is invented by Dean Oliver. Individual offensive ratings are constructed from the following two statistics:

  • Individual possessions, which represents the credit an individual gets for the times his/her team ends a possession and gives it back to the opponents.

  • Individual points produced, which represents the credit an individual gets for the points that his/her team generates on the offensive end.

 
Per Minute Ratings

The metrics that evaluates a player's performance more accurately than his averages.

The common notation for per-minute ratings is using per 40 minute stats.

Per minutes ratings are calculated by taking the player's total in any category (points, rebounds, assists, etc.) divided by total minutes played.

 
Player Efficiency Rating (PER)
Author: John Hollinger

The metric that which boils down all of a player's contributions into one number. John Hollinger's formula adds positive stats and subtracts negative ones through a statistical point value system.

For more information about PER Calculation visit basketball-reference


Comments: PER largely measures offensive performance. Hollinger freely admits that two of the defensive statistics it incorporates -- blocks and steals can produce a distorted picture of a player's value and that PER is not a reliable measure of a player's defensive acumen.
 
Player's Non-Scoring Possessions

A player's non-scoring possessions would be his missed field goals, plus free throws that weren't rebounded by his team, plus his turnovers.

Non-Scoring Possessions Formula=(Player's Field Goal Attempts)-Player's Field Goal Made)+0.4*(Free Throw Attempts)+(Player's Turnovers)

 
Player's Scoring Possessions
Author: Dean Oliver

A player's scoring possessions would be his field goals that weren't assisted on, plus a certain percentage of his field goals that were assisted on, plus a certain percentage of his assists, plus his free throws made.

Scoring Possessions Formula=(Field Goals Made) - 0.37*(Field Goals Made)*Q/R + 0.37*(Player Assists) + 0.5*(Free Throws Made)

where;

Q=5*(Player Minutes)*(Team Assist Total)/(Team Total Minutes)-(Player Assists) 
R=5*(Player Minutes)*(Team Field Goals Made)/(Team Minutes)-(Player Assists)

 
Player's Total Possessions
Author: Dean Oliver

The metric that represents a player's total possessions in the game. In other words,a player's total possessions is the total number of how many times he ends his team's possession.

Player's Total Possessions Formula=(Player's Scoring Possessions)+(Player's Non-Scoring Possessions)=(Player Field Goal Attempts)-(Player Missed Shots)*(Team Offensive Rebounding Percentage)+0.37*(Player Assists)-0.37*(Field Goals Made)*Q/R+(Player Turnovers)+0.4*(Player Free Throw Attempts)

Where;

Q=5*(Player Minutes)*(Team Assist Total)/(Team Total Minutes)-(Player Assists)
R=5*(Player Minutes)*(Team Field Goals Made)/(Team Minutes)-(Player Assists)
 

 

 
Plus-Minus

The plus-minus ratings simply keeps track of the net changes in score when a given player is either on or off the court.

 
Position Adjusted Win Score (PAWS)
Author: David Berri

The "Win Score" metric that takes player's "primary position played" into account.

PAWS=Position Adjusted Win Score=[(PAWS48/48)*Minutes]

PAWS48 =PAWS per 48 minutes=[WS48 – Average WS48 at primary position played]

WS48 =Win Score per 48 minutes

 
Seasons Left
Author: Dean Oliver

The estimate of how many seasons the player has left to play.

Seasons Left Formula=27-0.75*(Age of The Player) 

 
TENDEX
Author: Dave Heeren

Dave Heeren's player evaluation metric which is generally considered the first player rating system with linear weights.

The Tendex Formula=[(Points)+(Rebounds)+(Assists)+(Steals)+(Blocks)- (Missed Field Goal Attempts)-0.5*(Missed Free Throws)-(Turnovers)-(Fouls)]/(Player's Minutes)

 
Trade Value

The estimate using a player's age and his approximate value to determine how much value a player has left in his career.

Trade Value Formula=[(Approximate Value- 27-0.75*Age )^2( 27-0.75*Age +1)*Approximate Value]/190+(Approximate Value)*2/13

 
True Shooting Percentage

The metric that factors a player's performance at the free-throw line and considers their efficiency on all types of shots.

True Shooting Percentage Formula=(Player's Total Points)/[(2*(Player's Field Goal Attempts+ 0.44*Player's Free Throw Attempts)]

 
Usage Percentage

The metric that indicates the percent of a team’s possessions a player uses when on the court. The stats show that, for all players, as the player uses more possessions, his efficiency decreases.

Usage Percentage Formula=100*[(Team Minutes)/(5*(Player Minutes))]*[(Field Goal Attempts)+0.44*(Free Throw Attempts)+(Turnovers)/[(Team Field Goal Attempts)+0.44*(Team Free Throw Attempts)+Team Turnovers)]

 

By balancing usage rates and the varying offensive ratings of the five players on the court, a team can achieve optimal offensive output for the personnel.


Comments: What defines a superstar, in Dean Oliver?s statistical analysis, is that he can shoulder a larger proportion of a team?s possessions with only a relatively small drop in efficiency. Meanwhile, the opposite is also true: players perform more efficiently when they are asked to use fewer of their team?s possessions. As a result, the greater burden on the superstar means that supporting players maintain low usage rates, allowing them to operate closer to their peak efficiency.
 
WINVAL
Author: Jeff Sagarin, Wayne

A program which measures team chemisty and analyzes a player's impact on his team's ability to produce points. WINVAL is the labor of Jeff Sagarin and Wayne Winston, who are both graduates of MIT.

WINVAL's most unique characteristic is that it measures individual and team performance after every lineup change in every game. WINVAL's ratings also factor in who each individual is playing with and against at all times. The WINVAL scouting reports also include data on referees.

 
Win Score
Author: David Berri

The metric that indicates the relative value of a player's point, rebound, steal, turnover, and field goal attempt.

Win Score Formula=(Points)+(Rebounds)+(Steals)+(½Assists)+(½Blocked Shots)-(Field Goal Attempts)-(Turnovers)-½(Free Throw Attempts)-½Personal Fouls


Comments: Win Score is sufficient to give you a quick snapshot of a player?s performance. And it is especially useful if you wish to know if a player is playing better or worse than he did before.
 
Win Share

A Win Share is worth one-third of a team win. Win Shares are assigned to players based on their offense, defense, and playing time. If a team wins 60 games, there are 180 Win Shares to distribute among the players. This is always true; if a team wins n games, then there are 3n Win Shares to allocate to the players.

To get more information about Win Share calculation, click here

 
Wins Above Replacement Player (WARP)
Author: Kevin Pelton

WARP, a metric which is invented by Kevin Pelton, stands for Wins Above Replacement Player. The term and concept are borrowed from sabermetrics and, specifically, Baseball Prospectus.

Conceptually, the WARP system seeks to evaluate players in the context of a team made up of them and four completely average players. The performance of this team is then compared to that of a team made up of four average players and one replacement level player. The method also draws heavily on the work of
Dean Oliver.

Using replacement level shows the value of players who can play heavy minutes and avoid injury while continuing to perform above replacement level. Using wins gives a measure of value that is easy to understand and constant over time. Lastly, by eschewing the traditional linear weights method so common in basketball analysis, WARP does a better job of incorporating defensive value.


Comments: Like all rating systems based on box-score data, WARP cannot account for contributions that are not tracked in the box score, most notably on defense. It does no better than linear weights methods at evaluating players like Bruce Bowen. Also, it requires a number of assumptions - the value of assists, the trade-off between usage and efficiency, and replacement level.
 
Wins Produced
Author: David Berri

A metric which is invented by David J. Berri based on boxscore stats. Wins Produced is derived from the relationship between wins and offensive and defensive efficiency. It takes five steps to calculate Wins Produces for each player.

To get more information about Wins Produced calculation, click here


Comments: Wins Produced does a nice job explaining current wins and allows us to forecast.
 


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