This continues what’s turned into an ongoing conversation between myself and Nathan Walker (aka @bbstats) of the basketball distribution, which started with my last post, continued over at Nathan’s site, and has been supplemented on Twitter. I started by trying to find out the effect that turnovers have had on the Michigan State offense, which I did by calculating what was essentially an opponent-adjusted version of what Nathan later more intuitively converted to:
[Pts/Possession] – [Pts/(Possessions – TO)]
This tells us how much a team’s offensive efficiency would change if their turnovers all magically disappeared. Turnovers are a very simple case: there can be only 1 or 0 turnovers on each possession; and when there is a turnover, a team never scores on that possession. Contrast that with rebounds: in theory, a team could gain 20 offensive rebounds in one possession, yet not score; another team could score after every single offensive rebound. The only way I could think of to track this kind of thing is to look at play-by-play data, which can get extremely time consuming, extremely quickly.
Nathan came up with another way of looking at the efficiency impact of rebounding and the other Four Factors, though. He published an Excel spreadsheet (in this post) that uses a regression equation to ask, for example, “What would Arizona’s predicted offensive efficiency be if we changed their eFG% to the league average value of 48.5%, and what’s the difference between that value and their actual efficiency?”