Thursday, August 30, 2012

Preseason polls are worth exactly what you pay for them

It’s college football season again, and I am excited about the possibilities. Week one brings an excellent out-of-conference matchup between Alabama and Michigan played at a neutral site in Dallas that, according to preseason polls, features two of the top ten teams in the country. But are Alabama and Michigan really in the top ten, or are they coasting on their considerable reputations?


In evaluating whether teams are properly rated, the first thing that comes to mind is to simply compare preseason and postseason polls. The difference in rankings would show up as a positive (underrated) or negative (overrated) change from preseason to postseason. The weakness with this method is that it treats all spots as the same. A team rated 20th going into the season that finishes 24th would be a -4, just like a team that rated 1st going into the season and finished 5th. To me, the second miss should be more significant because the gap between the 1st and 5th best team in the country should be much larger than that between the 20th and 24th best teams (think of the far right of a bell curve vs. the area closer to the middle). Because of the system that adds weight to movements at the top it will be extremely hard for a team to show up as overrated without being in the top portion of the polls, but that seems like a reasonable proposition as a team starting in the high teens cannot be considered highly rated. Now we just have to think about the best way to systematically account for errors in different ranges of the poll.

In a previous post, I used the average postseason Sagarin points to account for the varying differences between teams from the top (larger gaps) to the bottom of the poll (smaller gaps). While using votes for each team is another option, it relies on the polls themselves – which we are examining for flaws – rather than a reasonably reliable third party. The Sagarin rankings are postseason but, in theory, that’s what the preseason rankings are striving for. Check out the demonstration of the dropoff in points from 1 through 25 displayed nearby (this will help provide context for the numbers in the tables below). Now that we have a methodology, let’s put it to work.

Wednesday, August 22, 2012

It's gotta be the suits (world records in swimming)

Ryan Lochte is smiling, but what about everybody else?

I am suffering from a bit of Olympics withdrawal, and getting quite a bit of pressure from someone, so I thought would write one more thing about an Olympic sport before they go away for four years.

Setting a world record in swimming is extremely tough these days. At the 2008 Summer Olympics in Beijing the eight 100 meter events (Free, Back, Breast and Fly for men and women) saw six world records set – three in the Men’s 100 Free alone. By comparison the 2012 London games witnessed only two world records in the same set of events. Factor in the 4x100 relays (Medley and Free) and the 400 IM and Beijing gets an additional six records for a total of 12 while London sees only two more to bring the total to four.

Of course back in Beijing swimmers could wear full body suits made of polyurethane, reducing their drag relative to bare skin and providing buoyancy. In the summer of 2009, as swimmers were setting records by the poolfull (get it?) at the World Championships in Rome, swimming’s governing body banned the suits effective January 1st 2010.

So what has all this done for the state of swimming world records? Were these suits responsible for the success or have swimmers found new ways to train that make those records achievable.

Sunday, August 5, 2012

Why does China win so many gold medals?

With the Games of the XXX Olympiad fully underway in London, I thought I would turn myself towards some Olympic numbers. I fully intended to do a look at declining records for speed across sports (swimming, track and field, cycling and so on) and still might get to it, but I was intrigued by a different statistic before I could get that effort off the ground.

China has become a dominant player in the Cold War-era game of topping the Olympic medal table. Since their return to the games in 1984 after 32 years – China boycotted the Olympics between 1952 and 84 due to the presence of the Republic of China, known in the IOC since 1979 as Chinese Taipei – they have won 385 medals in seven Summer Olympics. This obscures somewhat their recent run of strong results with 221 of those medals having come in the last three games. What prompted further inquiry was not the volume, however, but the composition of the total.