It's been almost three years since I posted my models to predict the three point accuracy of players coming into the NBA, a post called "Predictions Are Hard: Especially About Three Point Shooting". Along with presenting the coefficients for the models, I also gave the results for some of the first round selections from that summers 2014 draft class. (The results for some of this year's class are up at a Nylon Calculus post here).
The models were trained on the shooting percentage first four years a player is in the league, so we're not quite to the time frame to give an exact test, or, retrodiction of those projections. But, it's too close for me not to give a little look in.
To test the models I compared the mean average error (MAE) of model projections against the MAE of the player's pre-NBA (either college or overseas) three point percentage and the MAE compared to assuming the player is league average. The two models I presented performed virtually identically, both performing better than compared to he player's three point percentage and better than the simple average shooter assumption. The models had a MAE of 3% and 3.1%, while the MAE for the player's pre-NBA three point percentage was 5.7% and compared to the NBA average three point percentage the MAE was 4.2%.
The results for individual players featured in the original post are shown below, with their Pre-Draft three point shooting, NBA performance and the two models projections, then the error for each measure.
Overall this class has not been a good shooting class, with a 32.9% average player shooting percentage. Though slightly higher, 33.4%, if weighted for attempts. The models were slightly biased high compared to the actual performance projecting 34.9%, the player's pre-draft three point percentage was 35.7% and league average since 2002 at around 35.5% coming into this year. The biggest miss was on Adreian Payne, who never developed the three point shooting he needed to establish his game. James Young was a similar miss, under performing his projections in shooting (along with many other areas of the game).
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