Chad laments that we don’t hear that much about the decathlon any more, because Americans aren’t really competitive. I also think it’s a shame, because any sport in which your score can be a complex number deserves more attention.
Yes, it’s true. The decathlon combines ten different track and field events, so to come up with a final score we need some way to tally up all of the individual scores so that each event is of approximately equal importance. You know what that means: an equation. Let’s imagine that you finish the 100 meter dash in 9.9 seconds. Then your score in that event, call it x, is x = 9.9. This corresponds to a number of points, calculated according to the following formulas:
points = α(x0-x)β for track events,
points = α(x-x0)β for field events.
That’s right — power laws! With rather finely-tuned coefficients, although it’s unclear whether they occur naturally in any compactification of string theory. The values of the parameters α, x0 and β are different for each of the ten events, as this helpful table lifted from Wikipedia shows:
Event α x0 β Units 100 m 25.437 18 1.81 seconds Long Jump 0.14354 220 1.4 centimeters Shot Put 51.39 1.5 1.05 meters High Jump 0.8465 75 1.42 centimeters 400 m 1.53775 82 1.81 seconds 110 m Hurdles 5.74352 28.5 1.92 seconds Discus Throw 12.91 4 1.1 meters Pole Vault 0.2797 100 1.35 centimeters Javelin Throw 10.14 7 1.08 meters 1500 m 0.03768 480 1.85 seconds
The goal, of course, is to get the most points. Note that for track events, your goal is to get a low score x (running fast), so the formula involves (x0-x); in field events you want a high score (throwing far), so the formula is reversed, (x-x0). Don’t ask me how they came up with those exponents β.
You might think the mathematics consultants at the International Olympic Committee could tidy things up by just using an absolute value, |x-x0|β. But those athletes are no dummies. If you did that, you could start getting great scores by doing really badly! Running the 100 meter dash in 100 seconds would give you 74,000 points, which is kind of unfair. (The world record is 8847.)
However, there remains a lurking danger. What if I did run a 100-second 100 meter dash? Under the current system, my score would be an imaginary number! 61237.4 – 41616.9i, to be precise. I could then argue with perfect justification that the magnitude of my score, |61237.4 – 41616.9i |, is 74,000, and I should win. Even if we just took the real part, I come out ahead. And if those arguments didn’t fly, I could fall back on the perfectly true claim that the complex plane is not uniquely ordered, and I at least deserve a tie.
Don’t be surprised if you see this strategy deployed, if not now, then certainly in 2012.
August 19th, 2008 at 12:23 pm
I think this is my favorite CV post so far. Thanks for brightening my day.
August 19th, 2008 at 12:58 pm
What, the heck?!
Wouldn’t it just be easier to compare the athlete’s performance as a fraction of the world record for that event. So a 100 meters run in 9.9 seconds would score 9.69/9.9×1000 or 979 points. A 15 foot pole vault (4.57 meters) would be 457/614*1000 or 745 points and so on. That way a high school kid could keep track of his points against Olympians or against his country’s high school record.
August 19th, 2008 at 1:18 pm
More interesting is that, to a physicist’s level of accuracy, the power laws fall into three categories: running events (~2), jumping events (~3/2) and throwing events (~1).
This is screaming out for a Theory of Decathlon Unification.
August 19th, 2008 at 1:19 pm
Thanks for the laugh at the end.
August 19th, 2008 at 1:29 pm
@jmchez – it might be easier, but it wouldn’t be fairer. They’d probably based the power on the expected variability between high class athletes for that event – to make the total range of scores available for the 100m about the same as that for the javelin.
http://en.wikipedia.org/wiki/Decathlon_scoring_tables
“Beginning in 1920, the IAAF considered, at least, the following criteria for a legitimate decathlon scoring table:[2] (1) The table should reflect the fact that, at higher levels of performance, a unit gain (such as a decrement of 0.01 second in sprint times) is more significant than at lower levels of performance, because of the physiological limitations of the human body. (2) The scores for different events should be comparable, in a manner such that equal skill levels in different events (however difficult it is to define such a concept) are rewarded with equal point levels.”
August 19th, 2008 at 1:32 pm
Regarding the complex number bit of the original post – I’ll bet there is some bit of small print that says (if x>x0 for track, or x<x0 for field, then the score is Y)
August 19th, 2008 at 1:42 pm
Some great commentary on Olympic scoring.
What I would like to know is how Gymnastics can justify five significant digits (a score like 16.025) that are based on human judges giving out scores to two significant digits (a score like 9.1)?
August 19th, 2008 at 1:43 pm
[...] The following is blatantly stolen (and slightly adapted) from Cosmic Variance [...]
August 19th, 2008 at 1:57 pm
jmchez: well, they can still do that with this system, they just have to know a little algebra! (or use, say, a score calculator).
The scoring almost *has* to be nonlinear, because the marginal cost of improvement is different at different times – dropping a 18 second 100m time to 17 is much easier than going from, say, 10.9 to 9.9. Ideally, I’d think the reward should roughly correspond to the fraction of athletes with times in that region. Of course, everything is tweaked for historical reasons, and to make sure specialists can’t dominate.
According to this wiki page the throwing events used to have sublinear powers, essentially based on the idea that running speed and throwing speed should scale, but range scales like the square of velocity. The factor of two seems to have remained. Not sure how jumping factors in, though, James!
August 19th, 2008 at 1:58 pm
Haha. Hacking into the “flaws” of the decathlon formula!
Does it ever bother you that you can’t say A < B in complex numbers?
August 19th, 2008 at 2:03 pm
What if they take the *imaginary* part?
August 19th, 2008 at 2:04 pm
Further thought : I am surprised that the gaussian didn’t show up anywhere in their calculation of scores.
August 19th, 2008 at 2:19 pm
In the end, man races against himself, so it should be possible to “unify” the scores by simply referencing to how probable the exceeding of expected values was. Perhaps better to use one of the extreme value distributions instead of the Gaussian?
You could even reference them to different populations (e.g., the athelete’s home country) so that a fourth place finish by someone from Luxembourg would easily beat a first place finish by someone from China. Thus formalizing the usual Cool Runnings chatter.
One also would like to have some non-linear relationships here (e.g., two second-place finishes count more than a first place and a third place.) That way you could have a running of the couplings along with the athletes. Ha! I wrote this comment just for that joke.
August 19th, 2008 at 2:21 pm
I’m a decent athlete, but a lightweight who hadn’t thrown a shotput since the 8-pounders in jr. high. I competed in an intramural track meet in college and thought I’d do a full decathlon (which I actually did quite well in) sans pole vault. But when it came down to the full-weight shotput, I wasn’t prepared for how heavy it would be and actually threw a negative distance (inside the circle)! If they were doing proper decathlon scoring, I think I would have broken the system.
August 19th, 2008 at 2:23 pm
[...] of Foul Play in Olympic Gymnastics Take a look at how the Olympics scores track and field: The Hidden Complexity of the Olympics | Cosmic Variance __________________ "I stand by all the misstatements that I’ve [...]
August 19th, 2008 at 2:31 pm
It seems like the simplest solution would just be to change the formula to:
The idea of a complex number score is pretty amusing, though.
August 19th, 2008 at 2:32 pm
Oops! That should be:
August 19th, 2008 at 2:35 pm
Ah, they were sloppy in their function definition.
They mean, of course, to use a conditional function which looks like:
f(x) = …… if x gte 0
f(x) = 0 if x lt 0
This definition preserves continuity but not differentiability at x = 0.
Hence, were we to come up with some sort total energy use function, it would be a tough problem to maximize one’s score while holding the energy function to a fixed value.
August 19th, 2008 at 2:51 pm
Given the scoring for women’s gymnastics this year, I would suggest that the use of imaginary numbers is far from a theoretical construct.
e.
August 19th, 2008 at 2:57 pm
Elliot, boxing too. I’d just say that I wouldn’t want to get hit by some of those “non-scoring” punches.
August 19th, 2008 at 3:11 pm
LOL, and an idea is born.
Here i am, an irreverent, maybe jaded 200m runner who will, realistically probably finish last ( since someone has to ) and it’s my last Olympic appearance or maybe the best scenario is i have a slight injury which guarantees this loss, whatever. So, no medals, no sweet lucrative sponsorship deals with Nike after the olympics etc. So what can i do to salvage something from the situation ?
Run the race in s u p e r s l o w m o t i o n !
The uproar over such a publicity stunt would be considerable and certainly no small amount of ireverence and courage would be needed since these athletes are representing their countries and all so, this is why an injury basis is the ideal (perhaps ONLY ) “justification” for such a stunt. Nevertheless, if sponsorships and historical notoriety have a real world and legitimate role or value in the Olympic universe then i think such a stunt could succeed admirably.
August 19th, 2008 at 3:31 pm
Dan (#7),
Gymnastics scores aren’t really correct to the thousandth of a point. All the scores (in the Olympics, where there are six judges and the middle four count) are multiples of 0.025, since they’re obtained by averaging four scores which are each multiples of 0.1 (for the “execution”) and then adding another score which is a multiple of 0.1 (the “difficulty” of the routine). It’s just that they’re reported with three digits after the decimal point so that the numbers can be given exactly; it would perhaps be more confusing if they were rounded to two places after the decimal point, because then it would not be obvious that the gap between 16.00 and 16.03 is the same as the gap between 16.03 and 16.05.
I’m not sure why they don’t just add up the scores instead of averaging them, though. I suspect it has something to do with there being different numbers of judges in different competitions.
August 19th, 2008 at 4:28 pm
[...] to watching some random sport that we hardly knew existed, I’d like to direct you towards another brilliant post on the Cosmic Variance blog about some oddities in the point system of decathlon, and some ideas to [...]
August 19th, 2008 at 4:47 pm
Clever, but the simplest solution is probably to throw an (implicit?) step/Heaviside function in there.
Although the conditional with an absolute value mentioned above makes perfect sense, too.
August 19th, 2008 at 5:02 pm
Also, the individual event scores aren’t distributed throughout the complex plane. As long as you have a way to pick a unique branch of the logarithm/fractional power law the scores will be arranged along a single curve in the complex plane and it is possible to uniquely define an ordering along that curve. You could then define the score as a real parameter from some parameterization that lands you at the point on the curve designated by the above equations. The simplest parameterization is given above by TimG and ollie.
August 19th, 2008 at 7:38 pm
Maybe the solution would be to hand imaginary medals to the athletes with the greatest imaginary comaponents in their total scores.
August 19th, 2008 at 8:15 pm
OMG…. didn’t know about this system! Great post.
August 19th, 2008 at 11:31 pm
lol, gem of a post
August 20th, 2008 at 12:48 am
This post rules.
August 20th, 2008 at 1:27 am
I’ve said many times to anyone who will listen: when you are dealing with stuff where negative numbers don’t make sense, take a log. In the case of the decathalon, we would be talking about a weighted geometrical average. Makes far more sense.
August 20th, 2008 at 1:31 am
Thus, we get rid of alpha and x0, just keep the beta terms and *multply* the results together rather than adding them. For timed events, the betas would be negative, of course.
August 20th, 2008 at 11:13 am
@ jmchez (post #2)
“Wouldn’t it just be easier to compare the athlete’s performance as a fraction of the world record for that event?”
In addition to the comments presented earlier in this thread (the point system should be non-linear because it becomes harder and harder to improve your result when you get better and better), there is also the almost trivial fact that world records tend to evolve in time. What happens if the world record of 100m sprint improves while the decathlon competition is still going on? Will the points from the 100m run in the decathlon race change accordingly? What happens to the old decathlon results when the world records improve later on? How can you meaningfully compare results from different decathlon competitions (necessary if one wants to talk about the world record of decathlon) if the way athletes are rewarded points has changed?
In my opinion, those issues make it impossible to base the decathlon point system to the world records of the individual events.
August 20th, 2008 at 11:48 am
Oh, and I believe the world record quoted by Sean is off, the 9000 point mark was achieved already quite a few years ago.
August 20th, 2008 at 4:24 pm
[...] Olympic Math Thank the Science Department chair at work for this one. If you’re patient enough to understand the math, you might get a kick out of this site. [...]
August 20th, 2008 at 8:09 pm
I score this post at 1337. That was fantastic. Thank you for making me laugh. I have always thought that any event that needs a judge shouldn’t be an event, but it looks like every event needs a mathematical jury now.
August 20th, 2008 at 8:55 pm
In the currently highly competitive field of Olympics posts, this one wins. Fabulous (and educational). Thanks!
[I wonder whether there's some math basis for picking ten events that would make the 'best' decathlon, and what the criteris for such would be? Hmm.]
August 21st, 2008 at 3:54 pm
What do you mean that there aren’t any Americans who are competitive in the decathlon? Brian Clay is the reigning World Champion (and if you know anything about track and field, you know that the athletes respect World Champions as much as Olympic Champions). Here’s his resume:
2005 World Outdoor champion; 2008 World Indoor champion; 2008 Olympic Trials champion; 3-time USA Outdoor champion (’04, ’05, ‘08); 2004 Olympic silver medalist; Two-time World Indoor silver medalist (’04, ’06); 2000 NAIA champion; two-time NAIA LJ champion … not to mention that Chris Huffins (recently retired) and Tom Pappas (2003 World Champion) ….
August 22nd, 2008 at 2:14 am
#13 I did not get your joke – However I think you are correct in that there should be a score for “trying your best”
August 22nd, 2008 at 12:36 pm
[...] Cosmic Variance finds a hole in the math of the decathlon: If you run slowly enough, you can guarantee [...]
August 22nd, 2008 at 3:23 pm
Thank you, but I think I’ll stick with theBucky Katt point system.
August 23rd, 2008 at 11:13 am
The ranking system defies logic. A real super analysis on a real flop metric!
August 24th, 2008 at 2:18 pm
[...] Cosmic Variance talk about the use of complex numbers in scoring for the Olympics. [...]
August 26th, 2008 at 8:51 am
[...] win the decathlon by doing exceedingly poorly? Well, yes, but your scores would only count in the imaginary world. Filed under: Uncategorized — cleek @ 9:51 [...]
September 1st, 2008 at 5:14 pm
Hello… I tried to manually pingback to this entry, but it did not work, so I’ll have to go with the “poor man’s trackback” (need to do this at several bloggers’ entries – among other to-dos – being stuck here in St. Paul, too drained to blog, this might be a good time for that).
Trackback from Not going to take it anymore, University Blog
September 9th, 2008 at 3:57 pm
[...] Los juegos olímpicos terminaron, pero este linkito es imperdible: en el decatlón se pueden obtener… javier — Sep 09 2008 # [...]