Is Ye Shiwen's 400m IM performance in Olympics "anomalous" statistically? The 16-year-old Chinese swimmer Ye Shiwen swam more than 5 seconds faster than her personal best in women's 400m individual medley in London 2012 Olympics, winning her a gold. Her performance received high exposure to media and mixed comments, even some controversy. For example, Nature published a news report titled "Why great Olympic feats raise suspicions -- 'Performance profiling' could help to dispel doubts" and immediately raised great attention and a great number of reader comments. 
As an effort for myself to better
understand the issue and an exercise, I attempted a 'performance profiling' as what the
Nature news report's subtitle says.  What I did is to analyze the short-term
performance increase (or decrease) of top swimmers in 400m IM worldwide during 2011
and 2012, and try to see how Ye Shiwen compares to other good
performance improvers. I found there are more than 20 swimmers who are arguably better performance improvers than Ye. What's also worth noting is that Ye is at a particularly interesting spot that her performance is between the majority male and majority female swimmers. Probably not exactly a surprise given she's world's No. 1 in the event. See my summary: http://bit.ly/swimdata.
But I wonder if some of the critical eyes here can "cross validate" this approach.  What kind of factors should be examined in this kind of "performance profiling" for sports, and specifically for the Ye case?
 A: In the 1968 games in Mexico City Bob Beamon shattered the world record in the long jump with a jump of 29 ft 2 inches topping a world record that was under 28 ft at the time.  It took decades for any one to come close and finally break Beamon's record.  What explains it?  The high altitude meant thin air and less air resistence.  Yet no one else went over 28 ft that day including Beamon on his other jumps.  No one suggested that Beamon took performance enhancing drugs.  It was a statistical outlier.  Outliers happen.  Statistical analysis won't explain it.  But in your case it seems that you have taken a very sensible and pragmatic approach.  You look at similar performers over the same time period for the same event and found many that improved their best times by more than what this chinese swimmer did.  I think that supports the view that her accomplishment is not very unusual and should not be attributed to any external reason such as some form of doping which is what I imagine some people may have been intimidating.
