With the season finally underway, there are going to be a lot more basketball posts at the site obviously. And my posts are going to feature a lot of stats that you, the RCT reader, may not be familiar with. First off, it's important to know that's OK and we're all learning here, and advanced stats are not necessarily always the best way to analyze a problem. However, it is the method I think is usually best, and the method with which I am most comfortable, so advanced stats it is.
The term tempo free simply alludes to the fact that it addresses how many points a team scores per possession vs. how many it scores per game. A team that scores 80 points per game but runs up and down the floor probably isn't a better offensive team than a team that plays methodically but scores 70 points per game, even if its raw point totals are higher.
For the rest of the explanation, I'd like to borrow liberally from last year's primer:
For you TFS experts, feel free to skip. Or, better yet, comb through it and tell me how many mistakes I make. Granted, this isn’t a new thing. If you go to KenPom, read Basketball Prospectus, or read this man’s book on defense in basketball (published in 1959!) you have a good sense of tempo free stats. But for those of you to whom this is your first introduction, read on.
The basic crux of tempo free stats is thus: teams play at different paces. Especially in college basketball, where there are 300+ teams of varying skill level and depth. To call one 80 ppg team equivalent to another 80 ppg team is a misnomer. 80 possessions for each team (roughly) is what you would call a fast game and 60 (again, roughly) is what you would call a slow one. Last year the D1 average was 66.7 possessions per game. The fastest team was Alcorn State (77.6) and the slowest Denver (57.9)
How is it calculated? Glad you asked. Fortunately there are a lot of places out there to do it for you, but if you want to get an estimate, just use this equation:
FGAs – off. rebs + TOs + (0.475 x FTAs)
That’s it. Our crux for every calculation we come up with as far as offensive and defensive efficiency is concerned. Saying a team allowed 50 points per game is nice, but it means a lot more if it is Alcorn State allowing 50 ppg than if it is Denver allowing 50 ppg. This is why we look at points per possession (PPP, also called offensive/defensive efficiency), because it puts everyone on the same scale: how they do on each possession they have.
But advanced stats don't stop there:
For example: Let's take a look at why effective FG%, or eFG, is better than regular field goal percentage. The formula for EFG is (FGM + (0.5 x 3PM))/FGA, in order to give extra credit for making a three pointer. Let’s use this in an illustration: In 2009 Kansas was 2nd in the Big 12 with a 47.9 straight FG%, while Oklahoma State was down in 5th with a 45.7% mark. But, Oklahoma State had the edge in EFG 54% to 53.4%. Why? Well, for starters, the Cowboys took a lot more threes. They also made a lot more threes. The old saying goes, making a third of your threes is as good as making half of your twos. And it is basically correct. So, what you do with EFG is recognize that a three pointer is worth .5 more than a made two.
Turnover percentage, like PPP, uses turnovers committed per possession rather than per game to see just how well teams take care of the ball. The formula is simply TO% = turnovers/possessions.
Last year I looked at why rebounding margin is a terrible stat and why you should rely on rebounding percentage instead. To liberally quote from that post:
rebounding margin is the most flawed stat out there. To illustrate this, let’s take a look at the Baylor Bears. Topical, since they played just last night. Baylor currently leads the country in rebounding margin, at +11.4 per game. But a closer look reveals why. Baylor forces turnovers on just 17.2% of their defensive possessions, good for 324th overall in the country. This means that the opposition has many more shots to shoot, which naturally results in a lot more available defensive rebounds. And, since defensive rebounds are easier to grab than offensive ones, it artificially inflates Baylor’s numbers. In fact, Baylor is only 67th in defensive rebounding when calculating the percentage of opponents’ misses that they grab, which is the most important.
As Beadlemania hero John Gasaway posits, rebounding is really two skills: offensive and defensive rebounding. Defensive rebounding is the best way to compare how good two different teams are on the glass, because everyone tries equally hard to get defensive rebounds.
Offensive rebounds, however, are another story. Hard as it may be to believe, some teams don’t really try to get offensive rebounds. Take Colorado under Jeff Bzdelik. The Buffs are far more concerned with getting back on defense, usually leaving only one guy down low to try to grab an offensive board. This is a result of wanting to limit possessions. To wit, Colorado is 333rd in offensive rebounding this year and was 342nd last year. Staying in the Big 12, Kansas State still leads the country in offensive rebounding, at 43.5% Thus, rebounding margin can penalize teams that don’t try to go after offensive rebounds with the same vigor as other teams. We can argue the merits of this strategy another day, but the fact remains these teams are penalized for no reason in rebounding margin.
I don’t think I even need to tell you the last one: pace. Obviously teams that play fast are going to take more shots, which will result in more misses, which will result in more rebounds available. Take the Texas Longhorns. Texas is 6th in rebounding margin at +6.2 per game, and although they do well on the offensive glass, they’re merely adequate on the defensive glass, where more rebounds are available. This high rebounding margin is due to the fact that they are the 5th fastest team in the country. Northern Iowa is 104th in rebounding margin at +2.8 per game. However, they are much better than Texas on the defensive glass, only allowing the opponents to rebound 27.5% of their misses. This is because Northern Iowa plays at the 343rd fastest pace in the country at 60.9 possessions per game.
So there you go. How to be a good team in rebounding margin: play fast, don’t force turnovers, miss quite a few of your shots. I don’t want to give that team credit for much of anything, do you?
Finally, the last of the four factors is free throw rate. The formula for this is FTM/FGA.
Dean Oliver took a look at the four factors and which ones most closely correlate with winning games. eFG is by far the most important, turnover rate and rebounding rate are about half as important (with TO% being ever slightly more important) and free throw rate being the least important. In fact, there is a higher correlation between three pointers attempted and winning than there is with free throw rate. Not to say that getting to the line isn't important, just not as important as people would like you to believe.
Finally, individually. When discussing how good a player is, stick with the eFG, offensive rebounding rate, turnover rate, etc. Citing points per game is ok, but a better idea would be to go on a per minute basis. That way we can compare players who play 20 minutes per game with guys who play 30 minutes per game. It's not as smooth of a comparison as it is in the NBA, but generally players' production stays reasonably constant regardless of playing time. To get per minute stats you can go to Stat Sheet. (I wish it wasn't per 40 minutes, but we can't all get what we want or whatever that song is).
I think I have covered everything, but a quick recap: try to stick to per possession/rate stats as much as possible, never ever ever use points per game (on a team basis) or rebounding margin, and eFG > FG%. Any questions, feel free to ask.