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View Full Version : Assist % vs Assist Ratio



D-Will4Prez
10-15-2010, 05:33 PM
Thought this would be a good debate topic. What are the Pros and Cons of each? Benefits of using one vs the other?

I personally think Ast Ratio is a much more accurate representation of the player's set up/passing ability. What do you guys think?

arkanian215
10-28-2010, 01:50 PM
Assist Ratio = (Assists x 100) / [(FGA + (FTA x 0.44) + Assists + Turnovers]

Assist Percentage = 100 * AST / (((MP / (Tm MP / 5)) * Tm FG) - FG)

Looking at both of these, they both look to penalize guys who are more scoring oriented. If the game plan was for LeBron to go at the defender and look for his own shot more often, he would look like a less capable passer/creator than a LeBron who was told to set up his team mates.

I watched one of the highlights last night where Ariza got the steal, outlet it to Paul who was all alone and then Paul waited for Ariza to catch up so he could lay it off to him. That stuff only inflates his assist numbers. He could have very well made the layup himself so Paul didn't really "create" anything for Ariza.

The assist percentage does not penalize for turnovers. That's something I think is important when looking at passing ability. Of course, these turnovers aren't broken down into bad pass or just bad handles. It would be better if they broke turnovers into that. I like the assist ratio approach since it does use a bit of the per possession look.

There should be a better way to break down assists before looking at variations that try to define passing/creating ability. How much is a passer responsible for a layup attempt vs a jumpshot attempt? Non converted shots b/c of a miss or foul?

NJBASEBALL22
10-28-2010, 03:24 PM
I like straight up assist to turnover ratio. A/T.

DenButsu
10-29-2010, 06:09 AM
Assist Ratio = (Assists x 100) / [(FGA + (FTA x 0.44) + Assists + Turnovers]

Assist Percentage = 100 * AST / (((MP / (Tm MP / 5)) * Tm FG) - FG)

Looking at both of these, they both look to penalize guys who are more scoring oriented. If the game plan was for LeBron to go at the defender and look for his own shot more often, he would look like a less capable passer/creator than a LeBron who was told to set up his team mates.

But wouldn't that make him a "victim" of the game plan rather than the stats themselves? In those scenarios, both his assist ratio and % would be higher in the latter precisely because he'd be looking to assist on a greater share of possessions.

I think the main point is just to clearly identify what's being measured, namely that neither is necessarily a measure, specifically, of whether a player is a "good passer" or not, but rather... well, I'll re-quote patsSOXknicks, who broke it down in a way I think is really clear, when "NBA stats" was still a thread and not yet a forum:


Basketball-reference has Ast% vs. what they have on ESPN and Hoopdata with Assist Ratio. These are different statistics and they do have different meanings.

From basketball-reference


AST%
Assist Percentage (available since the 1964-65 season in the NBA); the formula is 100 * AST / (((MP / (Tm MP / 5)) * Tm FG) - FG). Assist percentage is an estimate of the percentage of teammate field goals a player assisted while he was on on the floor.
From ESPN


AST: Assist Ratio - the percentage of a player's possessions that ends in an assist. Assist Ratio = (Assists x 100) divided by [(FGA + (FTA x 0.44) + Assists + Turnovers]
Both of these stats are better then assists per game as that completely ignores pace.

A look at the league leaders:

http://www.basketball-reference.com/leagues/NBA_2010_leaders.html

http://insider.espn.go.com/nba/hollinger/statistics?sort=assistRatio&action=login&appRedirect=http%3a%2f%2finsider.espn.go.com%2fnba %2fhollinger%2fstatistics%3fsort%3dassistRatio

Pretty different. Why? Well upon closer look, the guys with really high Ast% have higher USG% too compared to the guys with just high Assist Ratios. Lebron is not even on the league leaders for Assist Ratio but he's 5th in Ast%- it's because he's 2nd in the NBA in usage rate. So he's going to Ast on a really high percentage of his teams FG because he's used more (and is obviously a good passer too) then say someone like Jason Kidd who doesn't have everything run through him all the time. So for the possessions that Jason Kidd is involved in, a very high % of them end in an assist but the % of the teams FG that he assisted won't be as high since his USG rate isn't as high and because Ast% is based on the minutes you're on the floor, not on the possessions in which you're involved in.

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All of that said, I agree, ark, that there probably are better ways to measure "passing quality" or "assist quality". I wish hoopdata did their "assists leading to... (at rim/3pointers/etc.) by possession rather than game.

PatsSoxKnicks
11-10-2010, 09:18 PM
All of that said, I agree, ark, that there probably are better ways to measure "passing quality" or "assist quality". I wish hoopdata did their "assists leading to... (at rim/3pointers/etc.) by possession rather than game.

Well Hoopdata does have totals, which means we can calculate by possession.

I'll use Felton as an example.

If we use the definition for a possession: [(FGA + (FTA x 0.44) + Assists + Turnovers]

Felton's numbers last year- 846 FGA, 173 FTA, 446 Assists, 123 TO's. So he had 1491.12 possessions last year. Round that to 1491.

They also have the assist totals leading to each location. So


at rim 10 ft 10-15 ft 16-23 ft 3fg
227 21 15 65 118
0.1522 0.0141 0.0101 0.0436 0.0791


The numbers at the bottom are the assists / total possessions (1491). So we have assists per possession.

Although obviously you have to do this out yourself if you're curious about the per possession stats. And I'm not sure why hoopdata doesn't do this themselves. Simple enough to calculate.

daleja424
11-16-2010, 03:13 PM
It makes sense to me to use a stat that tells you how often a player assists based on their possessions. It is important to include usage as a factor. A guy that plays 30 minutes in a game and has ten possessions for himself...and he walks away with 8 assists... has had a better assisting night than a guy who has played 40 minutes and gotten 25 possessions...and gotten the same assist total...

daleja424
11-16-2010, 03:20 PM
Just doesn make sense to me to evaluate the assisting ability of a player when they dont have the ball...