Re: A womans perspective on offensive rebounds
- Great information being provided here and by Stuart.
How do I use this info? It's explained somewhat here:
My formula has changed slightly from then (that was written in '96)
and the theory has advanced. But at a conceptual level, here is what
Offensive rebounds are an indirect contributor to a scoring
possession, somewhat like an assist, though an assist is even more
direct. An offensive rebound contributes to a scoring possession by
giving the offense another _chance_ to score, not a score itself.
For example, I'm looking at a recent Blazer-Sonic game (where
Portland won easily) where Portland shot 45/81 from the field and had
12 offensive rebounds. If you look only at how Portland did without
offensive rebounds, they scored on 54% of their "possessions" (called
a "Play %") = [FGM + (1- (1-FT%)^2)*0.4*FTA ] / [FGA + 0.4 * FTA +
TO], where FGM = 45, FGA = 81, FTA = 28, TO = 11, FTM = 20 (ft% =
0.714). If you look at how Portland did _with_ offensive rebounds,
they scored on 61% of their possessions ("floor %") FGM + (1- (1-FT%)
^2)*0.4*FTA ] / [FGA - OR + 0.4 * FTA + TO]. Basically, those 12
offensive rebounds turned into 6 new scoring possessions (~12 *
0.536, though my accounting says that some are probably duplicates).
I disperse that credit to individual scoring possessions according to
their offensive rebounds. I remove that credit evenly from all
player scoring possessions according to the assumption that they all
evenly benefit from team offensive rebounds.
Where all this detailed accounting from John and Stuart helps is in a
few areas. First, that play % is suggested to be a little bit higher
after offensive rebounds. If I adjust that in the formula, it gives
more credit to offensive rebounders than I currently give. Second, I
have assumed in my accounting even distribution after the offensive
rebound -- equal likelihood that anyone on the floor could score.
That definitely seems to not be the case from the detailed work.
This affects two things. It means that offensive rebounders are less
likely to have their made shots assisted on -- because more of their
made shots are after OR's, which are not assisted on. That helps
them. Second, I give half credit to the offensive rebounder and half
to "the rest of the team" on scoring possessions created by an
offensive rebound. (The ORFIG on the website said 0.1, but I worked
out the theory better to say that 0.5 works best in combination with
other changes I made.) This detailed work from John and Stuart is
suggesting that the "rest of the team" typically consists of that
offensive rebounder sticking it back. I need to work through the
theory to see whether I need to change that half credit to something
else. I don't think so, but I don't know.
Again, outstanding work you guys are doing. At some time in the not
too distant past, I felt like there was a serious lack of data to
help do detailed analysis. This is changing that. Now the
limitation is time to do the analysis.
Journal of Basketball Studies
--- In APBR_analysis@y..., "John Maxwell" <John.Maxwell@C...> wrote:
> Okay, maybe not a woman's perspective, but a perspective on the
> Over the past week or two, I've been trying to log all of the
> rebounds from last season in the WNBA to determine the importance
> offensive rebound to a team's offense. When I'm done, I'll have
> individual figures as well, but for now I thought I'd share what
I've got on
> a league-wide level.
> So far I've logged 2,012 of 5,056 offensive rebounds. My xl sheets
> grabbed the rebound, if the player that grabbed the rebound took the
> subsequent shot or turned the ball over, the kind of shot (two-
> three-pointer, free throws), the number of points derived from the
> rebound, if the player's teammates took the subsequent shot or
> ball over, the kind of shot, and the number of points derived from
> offensive rebound.
> Some things that aren't logged -- Whether or not the player that
> offensive rebound put the shot back up immediately or took the shot
> the possession as part of the offense, the kind of shot that was
> the shot clock at the time of the rebound, if the player who
> offensive rebound assisted on her teammate's subsequent field goal.
> there are other things that I can't think of that might have been
> looking into, but that's what I can think of off the top of my
> anybody has any suggestions as to if any of these things or other
> should be logged, I can look into it when I go back through to
check my work
> Dean, I'm particularly interested to see how this information might
> the credit given for an offensive rebound in your formulas.
> So with 40 percent of the rebounds logged, here's what I've found.
> In the WNBA . . .
> 57.2 percent of activity following the offensive rebound is
generated by the
> offensive rebounder. The offensive rebounder shoots the ball on 78
> of the activity that she generates, gets fouled and goes to the
> line on 13 percent of the activity she generates and turns the ball
> remaining 9 percent of the time.
> The remaining 42.8 percent of the activity following the offensive
> is generated by the offensive rebounder's teammates. Her teammates
> ball on 75 percent of the activity they generate, get fouled and go
> free throw line on 10 percent of the activity they generate and
> ball over 15 percent of the time.
> ----------------- Poss*--- FGA --- FTA --- TO -------3GA
> Orebounder --- 1150 --- 78% ---- 13% ---- 9% --------4%
> Teammates ---- 856 ---- 75% ---- 10% --- 15% ------14%
> I threw in the percentage of three-point field goal attempts there
> Success Rates
> Offensive rebounders are successful on 48.1 percent of their field
> attempts, 23.4 percent of their three-point field goal attempts and
> percent of their free throws. An offensive rebounders teammates are
> successful on 41.6 percent of their field goal attempts, 36.8
> their three-point field goal attempts and 68.0 percent of their
> -------------------- FG ----- 3G ----- FT ---- Pts/Poss
> Orebounder ----- 48.1 --- 23.4 --- 70.7 ------ 0.944
> Teammates ----- 41.6 ---- 36.8 --- 68.0 ----- 0.833
> Combined ------- 45.4 --- 33.9 --- 69.7 ------ 0.897
> Lg Avg ---------- 41.1 ---- 33.6 --- 74.1 ----- 0.815
> Lg Avg-Oreb --- 40.5 ---- 33.5 --- 74.8 ----- 0.805
> Lg Avg stands for the overall league average. Lg Avg-Oreb stands
> league average minus the possessions affected by an offensive
rebound - sort
> of a "First Shot" percentage. Since I haven't logged all the
> just assumed the same percentages for the remaining 3000 offensive
> to get a ballpark figure.
> Pts/Poss stands for points per possession. I counted each offensive
> as a new possessions despite the fact that most of us don't
consider it to
> be one since the ball never changes hands. I did this because it
> only way I could compare apples to apples with regards to how I was
> the offensive rebound data.
> Much of the data backs up what you might guess about the importance
> offensive rebound.
> Free Throw Percentages - the free throw percentages following an
> rebound are lower than the league average because taller players
> ones grabbing the offensive rebounds, and taller players are,
> the players who don't shoot as well from the free throw line. Dawn
> the WNBA's career free throw percentage leader, but she only
> offensive rebounds last season.
> The offensive rebounder hits a higher percentage of her shots than
> league average due to her proximity to the basket. She also takes
> fewer three-point field goal attempts for this same reason.
> The offensive rebounder's teammates hit a higher percentage of
> field goal attempts because everybody's attention is diverted
> Teams score more points per possession off of offensive rebounds
> Shot" possessions, even those possessions that are affected by the
> rebounder's teammates, although not by as much.
> Here are the hard numbers
> ----------------- Poss --- FG-FGA -- 3G-3GA -- FT-FTA ---- Pts -- TO
> Orebounder -- 1150 --- 430-894 ----- 11-47 ---- 215-304 --- 1086 --
> Teammates ---- 856 --- 266-639 ----- 64-174 --- 117-172 ---- 713 --
> Combined ---- 2006* -- 696-1533 --- 75-221 --- 332-476 -- 1799 ---
> *The possessions don't add up to the total number of offensive
> because a handful of offensive rebounds were credited right at the
> halves or the game where no additional shots were taken.
> That's all for now.
> John Maxwell
> Director of Public Relations
> Charlotte Sting