# Calculating NBA shooting consistency

What would be the proper way to evaluate/determine an NBA player's 3-point shooting consistency? For instance, I have a player that shoots 37% from 3-point range and takes 200 attempts all year.

I was considering taking the rolling average 3-point% of an arbitrary number of shots (say 20). Then using those averages to determine the standard deviation from the 37% mean. Using a rolling sample size of 20 shots only allows for a precision of 5% in shooting percentage, but I'm concerned that using too many shots won't reveal the inconsistencies in performance.

Is there a better approach to determine consistency?

• What are you going to use this measurement for? e.g. do you want to compare players to each other? Do you just want to see who is the most consistent? Or do you have some more specific question such as that consistency is higher when your team is ahead or something like that? – Peter Flom - Reinstate Monica May 17 '14 at 17:21
• I'm using the measurement to determine how consistent each 3-point shooter on a team is (of players that have some minimum number of attempts). I'll want to compare consistency between players, understanding that they'll have an unequal number of attempts in the season. – Will May 17 '14 at 19:18
• I think your basic idea is good. But why a rolling average? Why not "first 10 shots", "11th-20th" etc? You could try different numbers of shots. You should also probably limit this to players with at least a certain minimum number of shots in the season – Peter Flom - Reinstate Monica May 17 '14 at 19:23
• My thinking is that by taking the data in chunks instead of a rolling average, I might miss out on periods of inconsistent shooting. An extreme example being if a player makes shots 1-5, misses shots 6-15, and makes shots 16-20. Using 10-shot groupings results in two 50% shooting groups, but a 10-shot rolling average would reveal the 0% shooting slump. – Will May 17 '14 at 19:54
• Do an analysis of runs. Also, you need to be clear about what it is you mean when you say "consistent"--I'm going to interpret it as meaning that the probability of making a shot is constant for every single shot (i.e. it is completely independent of any and all previous outcomes). Agree? Nevertheless, do an analysis of runs... – Steve S Jul 22 '14 at 23:20