I was just revisiting Sabermatrician Consultant Sandy Weill's NBA shot model, thanks a Jacob Frankel piece on Hickory High earlier this week.
In short Weill used both the SportVu video tracking technology and the NBA's play-by-play data on 6,700 shots to create a model for expected shot value using a number of different variables, including shot type, the distance from the basket, defender proximity, and catch and shoot situations.
A couple of side notes from the model stood out to me as worthy of highlighting. One of the effects that the data did not show any value for was angle to the basket. In other words, straight on, right side, or left side did not matter, nor was there a difference between 45 degree or 90 degree shots.
That is really interesting information in the shot chart era. Shot charts are fantastic tools to convey a huge amount of information very quickly and elegantly. However, the more we slice and dice the court into pieces the smaller the sample size gets for each little piece, and inherently the less reliable the data.
For example, looking to update at my Scoring Versatility Index, I calculated that, based on the variation in three point shooting, it takes approximately 175 three point attempts to reach the player's 'true' shooting percentage (or at least the point where the sample has the same variation as the population). When we look at shot charts that divide three point shots into five zones including the two corners and three above the break three zones it is difficult to tell if the different colors right to left represent actual variation in a player's ability to hit shots or pretty random noise.
For example, here we see that Chandler Parson's is much better from the right side of the arc and particularly worse from the top of the key in his 2013-2014 shot chart via the great Vorped site.
Chandler Parson's Shooting 2012-2013
Or, maybe not. Looking at Chandler's shot chart from the previous 2012-2013 season, his worst location was from the right side and his best above the break location was from straight on the basket. The exact opposite of the current year. Maybe there is a plausible causation, for example, Parson's could be getting the ball in a different way or through different plays. But, really we should be cautious going beyond random variation without significant evidence.
Chandler Parson's Shooting 2013-2014
On the other hand, we do know that corner threes are, league wide, more likely to go down. And the Sabermatrician model gives us a pretty clear, if unsurprising, reasons why, it is shorter and more likely to be off of a catch and shoot, two factors that would account for the most of the advantage in field goal percentage for the corner three.
The shot model and write up is below the break.