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Team Evaluation Metrics


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There are 28 entries in the glossary.
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Term Definition
Assist Ratio
Author: John Hollinger

Assist Ratio is the percentage of a teamís possessions that ends in an assist.

Assist Ratio Formula=(Assists)*100)/ [(Field Goal Attempts)+(Free Throw Attempts*0.44)+(Assists)+(Turnovers)]

 
Balanced Scoring

The Herfindahl Index (HHI) can be used to measure scoring balances for NBA teams.

HHI calculation for each team: (1) divide each player's points scored by the total number of points scored by the team, (2) square that result for each player, (3) sum those squares.

 
Correlated Gaussian Winning Percentage

The method that relates winning percentage to points scored, points allowed, the standard deviations of points scored and allowed, and the correlation between points scored and allowed.

Correlated Gaussian Winning Percentage Formula=NORM{(Points Scored-Points Allowed)/[Standart Deviation(Points Scored-Points Allowed)]}
NORM means to take the percentile of a normal distribution.

 
Defensive Efficiency

The number of points a team allows per 100 opposing team possessions.

†Defensive Efficiency Fomula=100*(Points Allowed/Possessions)

 
Defensive Rebounding Percentage

The metric of a team's ability to get defensive rebounds.

Defensive Rebounding Percentage Formula=(Team Defensive Rebounds)/[(Team Defensive Rebounds)+Opponent's Offensive Rebounds)]

 
Effective Age

A metric that indicates the average age of the team, weighted by the playing time of players on the roster.

 
Effective Field Goal Percentage

The metric which combines 2-point shots with 3-point shots.

Effective Field Goal Percentage Formula=[(Field Goals Made) + 0.5*(3P Field Goals Made)]/(Field Goal Attempts) 

 
Efficiency Differential

The numerical gap between a team's offensive efficiency and defensive efficiency. The differential represents what each team did for the entire season and a teamís efficiency differential is a better predictor of future success.

Efficiency Differential Formula=(Offensive Efficiency)-(Defensive Efficiency)


Comments: Although efficiency differential does indicate the champion more often than just won-loss records, it's not perfect.
 
Four Factors
Author: Dean Oliver

Four factors are box score derived metrics that correlate most closely with winning basketball games. These factors also identify a teamís strategic strengths and weaknesses. Four factors can be applied to both a team's offense and defense, hence it gives us eight factors.

  • Shooting the ball

Effective Field Goal Percentage=(Field Goals Made) + 0.5*3P Field Goals Made))/(Field Goal Attempts)

  • Taking care of the ball

Turnover Rate=Turnovers/(Field Goal Attempts + 0.44*Free Throw Attempts + Turnovers)

  • Offensive rebounding

Offensive Rebounding Percentage = (Offensive Rebounds)/[(Offensive Rebounds)+(Opponent's Defensive Rebounds)]

  • Getting to the foul line

Free Throw Rate=(Free Throws Made)/(Field Goals Attempted) or Free Throws Attempted/Field Goals Attempted


Comments: While these are the four essential factors that decide winning and losing in the NBA, the factors do not carry equal weight.
1. Shooting (40%)
2. Turnovers (25%)
3. Rebounding (20%)
4. Free Throws (15%)
The number in parentheses is the approximate weight of each factor. Shooting is the most important factor, followed by turnovers, rebounding, and free throws.
Each statistic measures a separate skill ó thereís no reason that a team canít shoot well, commit few turnovers, rebound a high percentage of its misses and make frequent trips to the free throw line. At the same time, a team can compensate for poor performance in one area by outstanding performance in another ó hitting the offensive boards on a poor shooting night, for example.
 
Free Throw Conversion

The ability to get to the free throw line, and the ability to make free throws. Two metrics are used the measure free throw conversion.

(Free Throws Attempted)/(Field Goal Attempts) explains how often a team shoots free throws

(Free Throws Made)/(Field Goal Attempts) explains how well a team shoots at the line in addition to how often they get there

 
Log5

When two teams meet we can calculate the expected winning percentages using the Log5 formula.

WINNING PERCENTAGE OF TEAM A against TEAM B = W%(A)*(1 - W%(B))/(W%(A)*(1 - W%(B)) + (1 - W%(A))*W%(B))

 
Measuring Transition Defense

Dividing opponent fast break points by opponent steals might give us an idea of how teams execute "transition defense".

Transition Defense Metric=(Opponent Fast Break Points)/(Opponent Steals)

 
Measuring Transition Offense

Dividing fast break points by steals might give us an idea of how teams execute "transition offense".

Transition Offense Metric=(Fast Break Points)/(Steals)

 
Offensive Efficiency

The number of points a team scores per 100 possessions.

Offensive Efficiency Formula=100*(Points Scored)/(Possessions)

 
Offensive Rebounding Percentage

The metric†of a team's ability to get offensive rebounds.

Offensive Rebounding Percentage Formula=(Offensive Rebounds)/[(Offensive Rebounds)+(Opponent's Defensive Rebounds)]

 
Pace

The total number of possessions a team uses in a game.

Pace Formula=[240/(Team Minutes)]*(Possessionteam+Possessionopponent)/2

 
Play Percent

The metric that indicates the percentage of the time a team will score if not sent to the free throw line. Scoring possessions minus scoring possessions on which no field goal was made (only free throws), divided by possessions minus scoring possessions on which no field goal was made.

Play Percent Formula= Field Goals Made/(Field Goals Attempted-Offensive Rebounds+Turnovers)

 

 
Point Differential

The numerical gap between points scored and points allowed. Wins in close games tend not to reflect a team's true skill. Teams that start the season with a better record than their point differential tend to slow down and vice versa. Point differential is also a better predictor of future performance than win-loss record.

Point Differential Formula=(Points Scored)-(Points Allowed)

 
Points Off Turnovers

When a team commits a turnover, the scoring crew records the turnover. On the following opponent possession, if the opponent scores, the scoring system credits that opponent with a "point off a turnover.


Comments: Points off turnovers" is a misleading statistic. "Turnovers per possessions" is a better metric to measure the cost of a turnover
 
Possession

Arguably the most important discovery†in statistical analytics in basketball.†

A possession ends

(1)†by making a field goal attempt;

(2)†by missing†a shot and†not getting†the offensive rebound;

(3) by turning the ball over;

(4) by going to the line for two or three shots and either making the last shot or†not getting†the rebound of a missed last shot.

Two teams in any given game are essentially limited to the same number of possessions.

Basic Possession Formula=0.96*[(Field Goal Attempts)+(Turnovers)+0.44*(Free Throw Attempts)-(Offensive Rebounds)]

More Specific Possession Formula=0.5 * ((Field Goal Attempts + 0.4 * Free Throw Attempts - 1.07 * (Offensive Rebounds / (Offensive Rebounds + Opponent Defensive Rebounds)) * (Field Goal Attempts - FG) + Turnovers) + (Opponent Field Goal Attempts + 0.4 * Opponent Free Throw Attempts - 1.07 * (Opponent Offensive Rebounds / (Opponent Offensive Rebounds + Defensive Rebounds)) * (Opponent Field Goal Attempts - Opponent FG) + Opponent Turnovers)).
This formula estimates possessions based on both the team's statistics and their opponent's statistics, then averages them to provide a more stable estimate.


Comments: The .44 multiplier is because not all free throws take up a possession. Technical foul shots and "hoop and the harm"s do not, while there are more than two free throws on one possession with a three-shot foul. Research has determined that about 44% of all free throws take up possessions. The .96 multiplier accounts for team offensive rebounds in situations where a missed shot is tipped out of bounds by a defensive player, continuing the possession without an offensive rebound being credited.
 
Power Rankings

A subjective evaluation tool for the NBA teams which rates the entire league from top to bottom. NBA power rankings are based mostly on how good teams really are, with recent performances taken into partial consideration. The NBA.com does the power rankings job by using the offensive and defensive efficiencies.

Find out the NBA Teams' power rankings in graphics form which helps readers get a better understanding about exactly where the teams currently stand at.

 
Projected Winning Percentage

A formula that simply uses a team's net overall point differential (PD=points differential) rather than points scored and point allowed.

Each point of differential translates to 2.7 wins over the course of the season.

Projected Win%=[(Points Differential)*2.7)+41]/82

 
Pythagorean Winning Percentage

The method that gives an expected winning percentage using the ratio of a team's wins and losses is related to the number of points scored and allowed.

Expected Winning Percentage Formula=(Points Scored)16.5/[Points Scored)16.5 + (Points Allowed)16.5)]

 
Relative Percentage Index (RPI)

The Relative Percentage Index (RPI) is widely used to produce power ratings. Unlike most power rating systems, the RPI does not consider margin of victory or how well a team has played. It only considers whether a team won or lost. In fact, the RPI is based entirely on winning percentage.

It essentially measures a teamís strength of schedule and how a team does against that schedule. It is based 25% on a teamís winning percentage, 50% on the winning percentage of their opponents, and 25% on the winning percentage of their opponentís opponents.

Rating Percentage Index (RPI) Formula=.25*(Team's Winning Percentage)+.50*(Opponents'  Average Winning Percentage)+0.25*(Opponents' Opponents'  Average Winning Percentage)

For example if;
Atlanta is 4-1 (W/L Pct= .800)
Atlanta's opponents averaged a 12-8 (W/L Pct.= .600) record
Atlanta's opponents' opponents averaged a 64-16 (W/L Pct = .800) record, then,
RPI for Atlanta is = (0.25 * .800) + (0.5 * .600) + (0.25 * .800)=.700




Comments: It is best known for its use in college sports. Rarely is it mentioned in NBA circles because all teams play each other and most of the time people have fairly similar schedules.
 
Simple Rating System (SRS)

Simple Rating System (SRS); a team rating that takes into account average point differential and strength of schedule.

The rating is denominated in points above/below average, where zero is average. More information about calcution of SRS.

 
Strength Of Schedule (SOS)

Download NBA schedules in excel including rest days to build your own strength of schedule model!

Strength Of Schedule (SOS) represents a team's average schedule difficulty faced by each team in the games that it's played so far or for all season. The schedule difficulty of a given game takes into account the rating of the opponent and the location of the game.

Strength of schedule in the NBA has not been considered nearly as important as in the NFL or as in the NCAA basketball since the NBA teams play each other at least twice. Much of the schedule differences between teams come down to road trips, back-to-backs, afternoon games for example.

Strength of schedule can be calculated in many ways and all methods asssign a greater SOS number to a more difficult schedule.

Methods for Calculating Strength Of Schedule

SOS can be calculated by the help of Relative Percentage Index which incorporates W/L records of opponents and opponents' opponents. This method is being used by ESPN. John Hollinger explains the calculation of SOS.

Simple Rating System (SRS) also incorporates strength of the schedule by employing margin of victory (MOV) and the results can be found at basketball-reference.com

Another way used by Kenneth Massey is explained here.

Jeff Sagarin is also in charge of SOS ratings.

 
Turnover Ratio
Author: John Hollinger

Turnover Ratio is the percentage of a teamís possessions that end in a turnover.

Turnover Ratio Formula=(Assists)*100)/ [(Field Goal Attempts)+(Free Throw Attempts*0.44)+(Assists)+(Turnovers)]

 
Value of Ball Possession
Author: Bob Bellotti

Value of Ball Possession (VBP) is the leagueís average points per possession. If the NBA teams scored an average of 95.0 points per 100 possessions, that makes the VBP .95.

 


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