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View Full Version : A great thread for numbers nerds... why are ties so common?



Anthem
06-11-2009, 01:39 PM
Weird how often the differential between point scores is zero.

http://cheeptalk.files.wordpress.com/2009/06/histograminbantime.png?w=399&h=300

Explanation here:

http://cheeptalk.wordpress.com/2009/06/10/the-overtime-spike-in-nba-basketball/

count55
06-11-2009, 01:59 PM
Am I missing something, or are they just posing the question, but not really answering?

This was interesting:

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Does this prove that most (or more) teams that are ahead play not to lose, while most (or more) teams play with a greater sense of urgency when they are behind?

I wonder how "working the clock" comes into this equation. It starts to take off at about 20 seconds...once the game is tied, teams are more likely to bleed out the clock, not wanting to give the other team a chance. Teams are less effective late in the shot clock, generally...ramble, ramble...I need to track down some numbers.

BillS
06-11-2009, 02:39 PM
Look at what you are losing - the differentials right around that spike.

Essentially, this says that the standard strategies used by offenses who are behind by a small number of points can lead to a tie (or, interestingly, being ahead/behind by 6 to 8 points) more often than leading to a 1-4 point victory/loss.

Watch the end of the game with its deliberate fouls, timeouts that advance the ball, and so forth. The team that is ahead doesn't use fouls, though they may use the timeouts. They play not to give up a posession, so a quick shot is not in their best interest unless they are guaranteed to make it - you'll probably find that the team that is behind has more FGA (though not FTA) in those last 40 seconds. If the team that is ahead is able to hit 3s, then the margin increases beyond 1-4 points.

This seems more an indictment of free throw skills than anything else - it seems like missed free throws lead (anecdotally on average) to a 1-point cut in the lead. If the free throws aren't missed, I think you don't see this phenomenon.

It is interesting but I think it falls within the realm of explainable - it isn't a bell curve with a spike at a tie, it is a curve where there is a slight spike on either side of 1-4 points or so and a large one at 0.

Unclebuck
06-11-2009, 03:58 PM
me me me as I raise my hand

My answer makes perfect sense as to why there are more ties than there are 1 or 2 point games.

When the score is tied teams play it safe. If they have the ball they will run the clock down to the last possible tenth of a second (as to not give the other team a chance to get a decent shot) but by holding the ball until the last possible split second they often get a poor shot off so they miss. So they go into OT.

This is actually interesting. No not the numbers involved. But I would love to know the shooting percentage of a team when they are tied under 10 second, trail by 1, 2 and by 3. (Although the down by 3 numbers will be messed up because a lot of teams go for a quick 2 and are allowed to get a quick 2 and play the foul game)

I would also love to see the stats on whether it is better to be on defense leading by 1 or on offense trailing by 1 - also would need to break that down by seconds on the clock. I would think if there are less than 3 or 4 seconds it is much better to be on defense and have the lead. Whereas if there are 8 seconds left, maybe being on offense and trailing is better. (although my sense is that it is always better to have a 1 point lead) but I would still like to see the averages.


2 or 3 years ago, I think the Blazers local broadcast had a running stat during the game that I found FACINATING. They would calculate as the score changed, what the chances based solely on the current score of each team winning. Like when the home team leads by 10 with 8 minutes left in the 3rd quarter (the home team wins 65% of the time for example) - but at every point of the game they did that-

Slick Pinkham
06-11-2009, 04:50 PM
I would also love to see the stats on whether it is better to be on defense leading by 1 or on offense trailing by 1 - also would need to break that down by seconds on the clock. I would think if there are less than 3 or 4 seconds it is much better to be on defense and have the lead. Whereas if there are 8 seconds left, maybe being on offense and trailing is better. (although my sense is that it is always better to have a 1 point lead) but I would still like to see the averages.



Based upon offensive efficiency numbers such as points per posession, I'd also be surprised to find out that it's better to be behind with the ball at any stage. Teams average quite a bit less than a point a posession, and I doubt that this would change for posessions that began in the last 10 seconds or so of a game.

I remember offensive efficiency numbers coming up when "Hack a Shaq" was popular, and the fact of the matter was that if he was making 45% or more of his free throws, then he would be averaging 0.9 points per posession when he was fouled (shooting 2 free throws, making 45% of them). This is higher than the normal offensive efficiency of his team or of any team, really. Of course you also have the issue of getting your own people in foul trouble, getting the opponent into the bonus soon, etc.

I don't recall what the average team efficiancy is, in points per possession. I guess it depends on the definition of "posession" too. I consider an offensive rebound to result in a new possession, for example. I seem to remember 0.7-0.8 was the norm, but I may be off. My wife says I'm off, but that's beside the point. I digress...

count55
06-11-2009, 05:27 PM
Based upon offensive efficiency numbers such as points per posession, I'd also be surprised to find out that it's better to be behind with the ball at any stage. Teams average quite a bit less than a point a posession, and I doubt that this would change for posessions that began in the last 10 seconds or so of a game.

I remember offensive efficiency numbers coming up when "Hack a Shaq" was popular, and the fact of the matter was that if he was making 45% or more of his free throws, then he would be averaging 0.9 points per posession when he was fouled (shooting 2 free throws, making 45% of them). This is higher than the normal offensive efficiency of his team or of any team, really. Of course you also have the issue of getting your own people in foul trouble, getting the opponent into the bonus soon, etc.

I don't recall what the average team efficiancy is, in points per possession. I guess it depends on the definition of "posession" too. I consider an offensive rebound to result in a new possession, for example. I seem to remember 0.7-0.8 was the norm, but I may be off. My wife says I'm off, but that's beside the point. I digress...

Well, the average OffRtg in the NBA this year was 108.3, so that equates to about 1.08 points per possession...using the "calculated" methodology of arriving at "possessions":


Possessions (available since the 1973-74 season in the NBA); the formula for teams is 0.5 * ((Tm FGA + 0.4 * Tm FTA - 1.07 * (Tm ORB / (Tm ORB + Opp DRB)) * (Tm FGA - Tm FG) + Tm TOV) + (Opp FGA + 0.4 * Opp FTA - 1.07 * (Opp ORB / (Opp ORB + Tm DRB)) * (Opp FGA - Opp FG) + Opp TOV)). This formula estimates possessions based on both the team's statistics and their opponent's statistics, then averages them to provide a more stable estimate. The formula for players is rather lengthy and can be found in Dean Oliver's book.

The worst team in the league was the Clips at 102.3, the best: Portland at 113.9, so everyone, over the course of the regular season, averaged better than a point per possession.

The league hasn't averaged less than a point per possession since 1977, based on the statistical calculations published by BBR.com. I'm not sure why these are different from the numbers you are quoting.

ChicagoPacer
06-11-2009, 06:57 PM
The league hasn't averaged less than a point per possession since 1977, based on the statistical calculations published by BBR.com. I'm not sure why these are different from the numbers you are quoting.

The two of you are counting possessions differently. That's the difference between an estimate of close to 1.0 pt/poss vs. 0.7 pts/poss.

Using the 1 pt/poss definition of a possession, the possession only ends when you make a FG, make FTs, turn the ball over, or when the defense gets a rebound. This is the conventional stathead way of counting possessions.

Using the 0.7 pt/poss definiton, the possession ends in all of the above + an offensive rebound, which resets things to a new possession.

Using the latter results in a much higher possession count, but the same number of total points on the board at the end of a game.

ChicagoJ
06-11-2009, 07:12 PM
The advantage of the conventional way of counting possessions is that each team should have the same number of possesions per game (exception: when time expires.) If you count ORs as new possessions, then each team probably won't have the same number of possessions per game.

If this were football, you could ask it this way: is it a new possession every time the team gets a first down, or when the ball changes possession via score, turnover, punt, or end of half/game?

Hicks
06-11-2009, 08:08 PM
In basketball, I generally consider it a new possession if a team gets an offensive rebound.

Though if it were up to me, I'd only count it that way if the ball was reset on the perimeter. If the player just shoots again, I wouldn't. Not that both aren't a second attempt at scoring, but that one is a true "fresh start" and one isn't.

ChicagoPacer
06-12-2009, 12:10 AM
me me me as I raise my hand

My answer makes perfect sense as to why there are more ties than there are 1 or 2 point games.

When the score is tied teams play it safe. If they have the ball they will run the clock down to the last possible tenth of a second (as to not give the other team a chance to get a decent shot) but by holding the ball until the last possible split second they often get a poor shot off so they miss. So they go into OT.

This is definitely part of the reason. Another reason for the lack of 1 and 2 pt games is the trailing team's incentive to foul at the end of a game to lengthen the game. This tends to turn 1-2 pt games into 3-6 pt games. Refs also tend to swallow the whistle on a game ending decisive possession because they try to avoid making a call that would decide the game from the free throw line.

The last thing I can think of that reduces the number of 1 pt games is the risk aversion by coaches at the end of the game. If a team is trailing by 2 with 5 seconds left, more often than not teams are content with taking the 2 and trying to force OT. There are only two exceptions to the unwritten rule: 1-an out of bounds play designed for the 3 and 2-we're playing a better team on the road, so we might as well go for it.

Even if you're playing a precise equal, the strategy doesn't make sense. Assuming you will win 50% of your OT games, you might convert a 2 45% of the time, which means you will win in OT only 22.5% of the time when trailing by 2 in regulation. Assuming you can convert a 3 only 25-30% of the time, taking the three (and the 1 pt win in regulation) is the better strategy.

I think this is a psychological thing with coaches. If you take the three and make it, the player is the hero. If you take the three and miss, the coach gets second guessed on an aggressive play call. If you take the two and make it, it's still on the players to perform in OT. If you miss the two, you can at least say you took a higher percentage shot--even if it doesn't give you the best chance of winning.