Week In Review: Friday Apr 22nd

I took a break today from the retiring skier posts, but they will resume next Friday…

  • The first two parts of a brief season review for the North American skiers this week, focusing on the men’s and women’s distance skiers.
  • I did a little exploration of how we might put together some data on (very rough) FIS point benchmarks for developing skiers, based on a post by Pete Vordenberg here.

Week In Review: Friday Apr 15th

What a taxing week I’ve had…

Ha ha. Very funny. (It’s tax day in the US, for you foreign readers.) Thanks once again to Skaði Nordic for sponsoring this week in review:

  • A two part series examining the question of ‘home snow advantage’. The short answer is that while overall there is generally no (statistically) significant effect, there are noticeable differences between athletes and nations that are quite interesting.
  • A look back at the career of a great Italian sprinter who’s retiring this season, including some interesting stats that place her as one of the most consistent sprinters ever.

Week In Review: Friday Apr 8th

Gee, I wonder what the big news in XC skiing this week could be? It sounds from the translated reports from Norway and Estonia that I’ve read that Andrus Veerpalu tested positive (both A and B samples) for human growth hormone, but is denying any wrongdoing. Naturally, this means I started the week off with:

  • A new post revisiting my older one on Veerpalu. A common accusation against Veerpalu (and other suspected dopers) is that they have an unusual ability to show up at major events and ski much faster than they “normally” do. What I hope people take away from these two posts is that (a) our intuitive sense for “unusual” results does not always match the data, and (b) the answer you get will depend strongly on how you measure performance. The resulting situation is pretty ambiguous, which is why I would never recommend this line of reasoning as a serious accusation against someone.
  • A look at what we can learn about pacing from split times.
  • The first of several posts looking back at the careers of skiers who have decided to retire. This week was Pirjo Muranen’s turn.

Finally, I’m going to take this opportunity expand briefly on something I tweeted about. I read that one of the statements made at Veerpalu’s press conference in his defense was that he had passed more than 100 drug tests in the past. Although sports fans are becoming more educated about the statistics of drug testing, some confusion still remains. Without getting into the technical details, here’s the basic story.

Drug tests can make two types of mistakes: false positives, where we incorrectly label a clean athlete as a doper, and false negatives, where we incorrectly label a doped athlete as clean. In general, any testing scheme will involve a trade-off between these two types of errors. If you tweak your methodology in order to reduce the number of false positives, you will inevitably increase the number of false negatives. This trade-off cannot be outwitted! I often hear people suggest that maybe if we combine two, or three tests, or engage in some other complicated scheme, that you can reduce both types of error at the same time. Some testing procedures will be better than others in terms of both types of error, but whatever complicated combination of procedures and tests you invent, the end result will always amount to a single, big test that is itself subject to this very trade-off.

Drug testing in sports, for obvious reasons, is often calibrated in a such a way that false positives are considered far worse than false negatives. Specifically, tests are often constructed in order to be very careful to avoid falsely accusing an athlete of doping. Sadly, this means that negative results are simply less informative, in that they are much less likely to actually mean the person is clean.

My general conclusion as a stat guy is that I’m much more likely to believe that a single positive result is accurate than I am a single (or even many) negative results. A string of negative results doesn’t receive zero weight in my book, but they don’t receive much. (This is ignoring extra-statistical issues like mishandling samples at the lab, corrupt labs, or other similar human factors.)

Week In Review: Friday August 27th

It’s been a light week at Statistical Skier; had to move the Statistical Residence to a new (much improved) locale closer to work, so things have been a bit hectic.

  • We mucked around with the speeds that skiers travel at, looking at differences between races in Europe and the US.
  • A short not on rivalries, in which I unwittingly dissed Marcus Hellner’s sprinting ability.
  • Finally wrapped up XC skier retirement posts (really, honest!) with Tore Ruud Hofstad.


Week In Review: Friday August 13th

Cue the creepy music, it’s Friday the 13th!

I talked some friends into doing their first trail running race this weekend, so I’m looking forward to a nice 20 mile run in Montana’s Bridger mountains tomorrow.  Hopefully we’ll all still be friends on Sunday…

Week In Review: Friday August 6th

My Summer of Weddings continues this weekend, with some travel and a race to follow.  Fun times!  Here’s what we’ve acomplished at Statistical Skier this week:

  • Putting Distributed Sprint Points to good use we looked at the most unimproved male sprinters from last season.
  • Following a suggestion from a reader, I looked at whether there might be a relationship between a skier’s World Junior results and winning medals.  The results were murky.
  • We took a closer look at how Marcus Hellner faired versus his arch-rival Petter Northug last season.
  • Finally, we wrapped up the list of cross-country skier retirements with a look back at the career of Swiss skier Laurence Rochat.


Week In Review: Friday July 30th

What’s have you missed this week?  Read on and I’ll tell you…

  • We wrapped up some of the Tour de France graphs, even the fancy animated ones.
  • I demonstrated that there’s nothing special about the Tour de France, graphically anyway.
  • I’ve started putting my crazy contraption, Distributed Sprint Points to good use, looking at the most improved men and women in sprinting last season.
  • FasterSkier published a short piece of mine looking at what happens to skiers who’ve performed at different levels at World Juniors or U23s, and I followed that up with similar graphs for Canada and Germany (and more to come!).
  • Finally, we’re nearing the end of the list of retiring skiers, this week learning about the career of Milan Sperl.

Holy crap, I didn’t realize I posted this much stuff this week.

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