AllBuffs.com Intro To APBRmetrics
by, 11-01-2011 at 08:04 AM (10128 Views)
Welcome to the AllBuffs "Intro To APBRmetrics" area, or "How You Too Can Be A Stat Nerd". We're going to keep it simple, but this is going to discuss some stuff that we'll be discussing throughout the season when it comes to talking about the BasketBuffs. No more use of points per game for you. From now on, you're going to use words like "efficiency" and "tempo".
Everyone here has heard of "Moneyball", the book (now movie) of Billy Beane and how his use of Sabermetrics changed baseball. APBRmetrics is the basketball equivilent. Dean Oliver and John Hollinger both took Bill James' ideas for baseball and ushered them in to basketball using the internet. Basketball was more open to the idea of advanced stats than baseball was, with the Houston Rockets taking it to a new level in 2006 by hiring Daryl Morey as their GM.
TERMS WE WILL USE
The first four terms we will use are Dean Oliver's "Four Factors". These are considered the building blocks of APBRmetrics and efficiency. In other words, the better you are at these four things, the better your team is.
eFG% (Effective Field Goal Percentage): eFG% = (.5*3FGM + FGM) / FGA
eFG% was developed to take into account the fact that the standard FG% doesn't account for the extra value per shot for a 3 pointer. For example, shooting 33.3% from three point range over six shots would equal 2 makes/6 attempts and yield 6 points for the team. To get the same 6 points shooting from two point range, a team needs to shoot 50% (3 makes /6 attempts). To account for this, "effective" Field Goal percentage was born. An easy example from last year is Shannon Sharpe. Here are his numbers from last season:
FGM FGA FG% 3PM 3PA 3P% TS% 29 69 .420 1 15 .067 .428
So, for Shannon, we have the following:
(.5 * 1 + 29)/69 = 29.5/69 = .4275
Another example is Levi Knutson:
FGM FGA FG% 3PM 3PA 3P% TS% 158 312 .506 81 171 .474 .636
(.5 * 81 +158)/312 = 198.5/312 = .636
TO% (Turnover Percentage): TO% = Turnovers/Possesions
This one is pretty self explanatory. Basically, if you have the ball 20 times and turn it over 3 times, your turnover percentage is 15%. A turnover is a wasted possesion. The less wasted possesions, the more likely you are to score. Just think of this as the basketball equivilent of dating.
OR% (Offensive Rebounding Percentage): OR% = OR / (Offensive Rebounds for You + Defensive Rebounds for the Opponent)
This is the percentage of shots that you miss that you're able to get the rebound on. It basically is saying "hey, it's ok if you miss the shot if you're going to get the rebound". Now KenPom makes a good point in that this stat does NOT include "team rebounds" (where two or more guys fight over the ball), so it doesn't always line up perfectly with box scores, but it's pretty consistent overall. Let's use last year's game at Kansas State for an example:
CU Off. Reb 10 KSU Def. Reb 14
Using the formula, we get:
10 / (10+14) = 10/24 = 41.7%
And that right there tells you why CU won that game.
FTRate (Free Throw Rate): FTRate = FTA/FGA
This metric tells you how often you're shooting free throws, which is more valuable in the college game than it is in the pros. The more you can get to the line, the more "free" points that you get. Let's use last year's Texas game for an example:
CU FTA 32 CU FGA 60
Using the formula, we get:
32/60 = 53.3%
And that's how we won the Texas game.
Now along with the four factors, there are three other terms you're going to see us use regularly. They are much easier.
Offensive/Defensive Efficiency = Points Scored * 100 / Possessions
This is just telling you how many points your team would score/give up if there were 100 possessions in a game. You will not see possessions listed in the box score, so I usually just rely to the people who are much smarter than I like Ken Pomeroy to inform me of these stats. For our example, we'll use a hypothetical game in which there are 67 posessions (which is right around the national average from last year):
Colorado 75 Arizona 72
For offensive efficiency, we would have:
75*100 / 67 = 111.9
For defensive efficiency, we would have:
72*100 / 67 = 107.5
The national average last year was 101.3, so this would be considered a great game for CU's offense, but a below average one for the D.
Pace is the last term we will use and it just basically tells you how many posessions a team has in a game. This is used for the efficiency stats mentioned above.
There is a wealth of info out there, however it all starts with KenPom.com. Basically, if you can use KenPom for the basic info, you're set. Everyone should bookmark his site now.
Basketball Reference also has a college basketball section. I prefer the site for NBA info, but the college basketball stuff isn't bad either and is worth a bookmark.