Effective Field Goal Percentage

Brian Williams, The Coaching Toolbox.

Statistical analytics is playing a much bigger role in basketball at all levels and I think is going to continue to play a bigger and bigger role in how coaches evaluate their teams in both games and practices, how they develop their systems of play, and how they scout and prepare for upcoming opponents.  Here is one thought on having a more useful statistic than straight shooting percentage.

I used to look at a player’s scoring effectiveness as being ineffective if they did not score at least one point for each field goal attempted.  Defensively, we felt that if we held the other team’s top scorers to less than a point a shot, we had a great chance to win.  That also meant that we were not fouling and they were not getting to the line.  One of our player’s (who is now a coach by the way) said that when using this method of evaluation, free throws made were “extra credit” because they didn’t count against the shots taken..

However, that criterion was not very effective in evaluating our team’s performance.  If a player that was not one of our top scorers, or one who didn’t get a lot of playing time, took 4 field goal attempts, he needed to score at least 4 points to not be a negative for our offense.

But, I didn’t like it to measure our leading scorers. If our leading scorer took 18 shots and scored 17 points, that met the criteria that he wasn’t “hurting the team”, but that performance was not going to win against quality opponents.

Here is one stat that I have found to be much more useful in evaluating who are our most efficient scorers from the field.

EFFECTIVE FIELD GOAL PERCENTAGE

I first read about Effective Field Goal Percentage in Dean Oliver’s Book “Basketball on Paper: Rules and Tools for Performance Analysis

In my opinion, when looking at statistics, Overall Field Goal Percentage is not a useful statistic to judge your player’s shooting efficiency since it combines both two and three point shots to calculate the percentage.  Individual two point percentage and individual three point percentage will tell you how a player does at both ranges separately.  But, to get a comparison of how effective a player is who shoots mainly twos compared to a player who shoots mainly threes is the old apples to oranges comparison.

What you really want to know is: Who is producing the most points for your team for each shot that they take.

To accomplish that, Effective Field Goal Percentage is a more useful statistic than Overall Field Goal Percentage to use.  Effective Field Goal Percentage counts every three point shot made as one and a half makes since each three point shot scores one and a half times the number of points that a two point shot does.  It provides for a more level comparison for which players are scoring the most efficiently from the field. 

It gives you a scoring percentage as opposed to a “shots made” percentage.

The formula for effective field goal percentage is:

eFG% = (2FGM + 1.5*3PFGM)/FGA

2FGM = Two point field goals made
3FGM = Three point field goals made
FGA = Total field goals attempted (including both two and three point attempts)

In words, multiply the 3 point field goals made by 1.5. Then add the two point field goals made.  Take that total and divide it by the total number of field goals attempted (both 2s and 3s) to determine the Effective Field Goal Percentage.

Again, The reasoning used for multiplying three point shots made by 1.5 is that each one counts as one and a half as many points as does a two point shot.

Here is an example.  A player is 4 for 9 on 3 point attempts and 5 for 10 on 2 point shots.

4 three point shots made * 1.5 = 6.  Then, add 5 for the two point shots made which gives us a total of 11.  Divide that by the total number of field goal attempts which was 19.  The Effective Field Goal Percentage is 11/19 = 57.9%.

The player’s Overall Field Goal Percentage is 9 shots made on 19 attempts which is 47.4%.  In my opinion, that percentage is deceiving as to how much that player really helped your team from the field.

A  player shooting only two point shots and no threes would have to shoot 58% to be more “effective” from the field than the player in the example.

The first few times I looked at Effective Field Goal Percentage (EFGP), it was a little confusing (and my undergrad degree is in math J ), But after looking at it closely, it made more sense as a measure than the traditional overall field goal percentage.  It allowed me to compare how well we were scoring from the field and which players were the most effective from the field.

I will have another post soon that will detail “True Scoring Percentage” which is a stat that takes into account a player’s ability to get to the line and score, combined with scoring efficiency from the field.

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