Here is a list of some of the statistics I use most often for your (and my) reference. It’s helpful to me so I thought I’d share.

Each entry has the following:

- Name of the metric
- A description of what it’s used for
- The question it answers
- A more technical definition
- The formula itself
- A link to a description from someone more intelligent than me.

Please add any corrections, questions, or suggestions in the comments section.

Assist ratio: Used most often for point guards, assist ratio can be considered a proxy for passer decision making or a means to understanding the degree to which a player facilitates scoring opportunities for others. How often does a player create an assist? The formula is an opportunity rate that describes the percentage of plays on which a player creates assist. Ast/(Ast + (FGA + .44*FTA + TO)). Read more >>>

Assisted field goal percentage: Used primarily for teams, assisted field goal percentage tells us how often a team’s scoring opportunities were facilitated by a pass. What percentage of shots were created by an assist? The formula describes the number of assists per field goals made to give us the percentage of assisted shots out of all shots taken. A/FG. Read more >>>

Boxscores: Used for all players, Boxscores tell us how much an individual contributes to team wins. What portion of team wins can be attributed to a given player? The formula describes a player’s valuable contributions to the team in terms of team wins. Click for the formula and to read more >>>

Chaiken Efficiency Ration: *(see "points per empty possession" below)*

Defensive plus/minus: Used to measure a player’s defensive impact in terms of the difference between points scored when they are on the court and off the court (therefore positive numbers indicate a positive defensive impact). How much does a player influence the opponents’ ability to score? The formula describes the number of opponents’ points scored per one hundred possessions when a player is on the court vs. off the court.

Defensive value: Used to approximate a player’s defensive value to her team based upon blocks, defensive rebounds, steals, and personal fouls. How valuable is a player to her team defensively? The formula describes the value of a player’s defensive contributions per 40 minutes. ((dreb * .511 + stls * 1.60 + blks * .98 + pf * -.22)/minutes) * 40. Read more >>>

Diamond Rating: Used to approximate a player’s capacity to increase their statistical production if they played more often. How much more would a player produce if she got more minutes? The formula describes the difference between a player’s current production and expected production given their current minutes played and estimates their level of production with increased minutes. R*40 - R*Min/G + (R - leagueR)*40. Read more >>>

Effective field goal percentage: Used to measure a player’s shooting ability in terms of field goals and free throws. How well does a player shoot when taking free throw shooting into account? The formula describes the percentage of field goals and free throws made per field goal attempt. eFG% = (FGM + .5*3PM)/FGA. Read more >>>

Free throw rate: Used to measure how often a team (or player) gets to the free throw line for every field goal attempted. How often does a team get to the free throw line? The formula describes the percentage of free throws made per field goal attempted. FTA/FGA. Read more >>>

**Marginal Victories Produced (MVP)**: This measures "value" in terms of how much credit an individual player deserves for a team's wins. How much does a player contribute to a team's success? The formula is the player's production divided by *both* teams' overall production. It is described by David Sparks at Hardwood Paroxysm. (Note: the difference between this and Boxscores is that it works at the level of games or a series of games whereas Boxscores works best at the season level)

Net Plus/Minus: Used to describe a player’s net impact on the game’s score. How does a player's presence impact the game score? Read more >>>

Offensive rebounding rate: Used to measure how well a team gets available offensive rebounds. How often does a team get an offensive rebound? The formula is an opportunity rate that describes a team’s offensive rebounds per total rebounds available as calculated by their offensive rebounds and the opponent’s defensive rebounds. Team OReb% = TmOReb / (TmOReb + OppDReb) Read more >>>

**Percent valuable contributions (PVC):** PVC measures "value" in terms of how much an individual player contributed to a team's overall statistical production. How much of the team's statistical production did an individual player account for? The formula is simply to divide the player's production to the team's overall production, with production defined by Model Estimated Value. It thus defines "value" as a ratio of an individual player's production to the team's total production. It is described by David Sparks at Hardwood Paroxysm and there's an illustration of how it might be used to compare players in this analysis of 2010 WNBA MVP candidates.

**Points per empty possession (or points per zero point possession or Chaiken efficiency ratio)**: Used for individual players, points per empty possession could be considered as a proxy for scorer decision making or a means to understand how efficiently a player manages scoring opportunities. Points per empty possession is the ratio of points a player is individually responsible for to the possessions that a player is individually responsible for ending without points. It’s a proxy for scoring decision making – if a high usage player is able to create points more often than they waste a scoring opportunity, we can say they are making good scoring decisions. How often is a player individually responsible for the added value of scoring possessions and the cost of non-scoring possessions? The formula describes the number of points a player scores per missed field goals, missed free throws, and turnovers. Pts/(FGx*.693 + FTx/2*.693 + to).

Pure point rating: Used mostly for point guards, pure point rating can be used as a proxy for point guard quality by approximating the rate at which a player creates scoring opportunities for others. How well does a player balance the benefit of creating an assist with the cost of creating a turnover? The formula describes the net value of scoring opportunities a player created for teammates per minute played. 100*((ast*2/3)-to)/mins (not pace adjusted). Read more >>>

SPI Player Styles Spectrum: Used to describe the type and quality of each player in terms of scoring, perimeter skills, and interior skills. What type of player is she and to what degree does she exemplify that type? The formula describes the degree to which a player is a scorer, perimeter play-maker, or interior play-maker. For the formula and to read more >>>

Synergy rating: Used to describe the type of offense a team plays in terms of ball movement and individual play. For example, in the NBA, a score of 60-70 is indicative of a team that relies heavily on individual play, a score of 70-75 is a team that balances individual scoring and ball movement, and a score of 75+ is indicative of a team that relies heavily on ball movement to create scoring opportunities. (It’s important to note that while a team’s synergy score is a descriptive statistic, an opponent’s synergy score can explain how well a team disrupted their opponent’s offense.) In the WNBA, those numbers are higher, illustrating the game's heavier reliance on ball movement. How well does a team share the ball to find scoring opportunities compared to an emphasis on one-on-one play? The formula simply adds a team’s assisted field goal percentage to their effective field goal percentage to approximate how well they move the ball to create quality scoring opportunities. A/fg +eFG%. Read more (on this and "adjusted synergy") >>>

True shooting percentage: Used for players or teams, true shooting percentage describes a team’s field goal, three point, and free throw shooting. How well does a team shoot when taking free throw shooting and three-point shooting into account? The formula is a ratio of points scored per total field goal attempts and free throw attempts, thus accounting for the additional points scored on three pointers. TS% = Pts/(2*(FGA + (.44*FTA))). Read more >>>

Turnover percentage (team): Used for teams, turnover percentage describes the percentage of possessions on which a team turns the ball over. How often does a possession end with a turnover? The formula describes the number of turnovers per possession for a team or player. TO/(FGA - OR + TO + 0.4 * FTA). Read more >>>

*(Note: this number is actually different for players and teams -- for teams it's an estimate of possessions so you subtract offensive rebounds because those technically extend one possession. For players, you can look at that or the percentage per 100 plays => 100 * TOV / (FGA + 0.44 * FTA + TOV).)*

Usage percentage: Used to describe how often a player tries to create a play for their team – scoring or turning the ball over -- while on the court. The theory goes that having the ball in position to create any type of play is indicative of either ball dominance or a team’s faith in a player’s ability…which is why it is best used with some indicator of efficiency. How often is a player involved in making a play for their team? The formula describes the percentage of a team’s plays that a player is individually responsible for while on the court. For the formula and to read more >>>

Valuable Contributions Ratio: Valuable contributions ratio measures "value" in terms of an individual player’s efficiency in making contributions to the team while on the floor, independent of team success. How much does a player contribute when she is on the floor? It’s a ratio of player production to team production and it captures productivity relative to the time allowed for production. David Sparks describes the basis for the "production" aspect of this statistic at Hardwood Paroxysm.

Relevant Links

Basketball-Reference.com glossary:

- http://www.basketball-reference.com/about/glossary.html
- http://www.basketball-reference.com/blog/?p=1120

NBA Stuffer Basketball Research glossary: http://www.nbastuffer.com/component/option,com_joomap/Itemid,69/

Storm Statistical Analysis Primer: http://www.wnba.com/storm/news/stats101.html