NBA Draft – The Lottery

Now, the lottery. Fourteen ping pong balls – numbered 1 through 14 – are placed in a glass drum and well mixed for 20 seconds. Four balls are collected from the mix at ten second-intervals. So why 14 balls? The clue: it is not related to the 14 teams that are participating in the draw! But it has to do with statistics – Four balls, picked randomly from fourteen balls, gives a total combination of about 1000.

_{14}C_4 = \frac{14!}{4! 10!} = \frac{14 * 13 * 12 * 11}{4*3*2} = 77 * 13 = 1001

Each team gets a list of four-ball combinations (the look-up table) based on their assigned probability, as seen in the earlier post. E.g., Pistons, Rockets and Spurs get 140 numbers, the Hornets receive 125, Pelicans 5 etc.

Here is the list of the first 140 numbers generated by the R command, combinations(14,4)[1:140,]. It is just an illustration, and I am not sure if NBA assigns numbers in this order.

Once the team that qualified for the first draft is determined, the lottery is repeated. If a combination corresponding to the already selected team comes up in the draw again, the machine will be reset for another try.

References

2022 NBA Draft Lottery Presented By State Farm: NBA
The room where it happens: Behind the scenes at the NBA Draft lottery: The Athletic
How NBA Draft Lottery Probabilities Are Constructed: Squared Statistics
Nervous energy, phone withdrawal and a waiting period: Inside the 2022 NBA Draft Lottery drawing room