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886Re: [APBR_analysis] Re: touches per minute

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  • bchaikin@aol.com
    Apr 24, 2002
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      Let me also ask whether the factor matches what you would see in a
      game.  For instance, if we calculate a player's touches per minute to
      be 2 per minute, would that mean that, if he played 35 minutes, he
      would touch the ball, on average, 70 distinct times in those 35
      minutes? 

      yes - but my original research/analysis took place over the span of 3 seasons in the late 80s / early 90s, watching just under 1000 NBA games on tape, charting team and individual player ball possessions. the formulas are extrapolated from this data and streamlined for each season and each team (based on avg team yearly possessions and then each team's calculated possessions)...

      I ask because the formula seems to not include rebounds.  Obviously,
      guys touch the ball when they get rebounds.  If X and Y are team and
      year specific, then it is possible to have a couple guys with very
      different rebounding totals with similar possession factors.  For
      instance, Jon Barry and Ben Wallace aren't terribly different in the
      main factors you list.  Wallace has lower totals in all but FTA.  But
      he had  800 more rebounds than Barry.  How do these guys stack up? 

      think about it...to calculate how often a player handled the ball on offense you either have to count all the times he first gained possession of the ball while on offense, or what he did with the ball (how he got rid of it) each time he had the ball...again, what can a player do with the ball once he has it in his hands? he can either shoot it, pass it, get fouled, or turn it over (FGA + AST/X + FTA/Y + TO). other things can occur (off foul, double fouls, jump ball, techs, etc) but these occur only occassionally such that they can be ignored - if they were all measured they could be included...

      or how can a player gain possession of the ball while on offense? he can either start the team possession (get a pass from a player from out of bounds after the opposition has scored), start the team possession by catching an inbounds pass on an out-of-bounds play, simply receive a pass from another player on the court, or get an offensive rebound. i do not use def rebs because rarely does a player score immediately after getting a def reb (players do occassionally get rebounds, dribble the length of the court, and score, but the total # of times is insignificant compared to the total possessions and this parameter is tough to measure. if we had these numbers they could be added)..

      as for barry and wallace, i just uploaded the 01-02 reg seas stats to the online database so you can compare them there. just limit the database to the 01-02 season, and sort by possession factor, and you'll see how two players can have the same possession factor but different stats that when added up and divided by minutes played equal similar touches-per-minute ratings (poss fact)...

      also you can have two players with absolutely identical stats from two different seasons and they could easily have two different possession factors - because part of the rating is based on league averages. a simple example is shot blocking - two players can have the same # of blocks and minutes played in two different seasons but have their shot block rating vary by as much as half a percent or more based on what the rest of the league did that specific season. example - this past season jermaine o'neal blocked 166 shots in 2707 minutes and had a shot blocking rating of 3.6% (he blocked 3.6 of every 100 shots taken by the pacers opposition). in 1978-79 rich kelley of the jazz blocked 166 shots in 2705 minutes but had a shot blocking rating of only 3.2%....

      What was the original goal of the stat?  Is it better to say that it
      is an estimate of touches on the offensive end?

      the goal was to determine exactly how often each player handled the ball on offense so the computer could model the game, i.e. knowing how often each player handled the ball on offense and what he did with it (how often he would shoot, pass, get fouled, TO) once he did get the ball makes for an easy model for the computer to simply play a game...

      are the formulas "secret"? not really. complicated? not at all - four parameters (statistical categories - FGA, TO, passes, times fouled) and two variables. but there are upwards of 30+ formulas per season (one for each team), every season, although each is quite similar. you can actually back calculate them using the possession factors listed in the historical stats database at the APBR website or at www.bballsports.com....

      the best way to explain this would be to download a copy of the sim software i developed (members.aol.com/bchakin)  - again its free - and when you run a full season for any team it charts ALL ball possessions such that they can be added up easily. this is the best way to see "possession factors" or "touches per minute ratings" in action. plus the online stats databases lists possession factors for every player since 1977-78 for the NBA and even earlier for players in the ABA...

      bob chaikin
      bchaikin@...

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