Friday, 16 December 2011

Two Become One

In the previous post I looked at the HHP leaderboard and discovered some interesting patterns regarding certain teams.

It looks as the evidence proved out to be true, with SD_John and Lily now all of a sudden merging into a single team.

Interestingly they have also been in other competitions with very similar results.

This was the final standing in the Give Me Some Credit competiton,

What is actually more interesting here is the demonstration of overfitting to the leaderboard. Opera Solutions & JYL are more than likely working together and we know Lily & SD_John are working together. If you look at the leaderboard just before the competition ended (on the 30%) you will see Opera near the top but the final position on the 70% was much worse. Similarly a few others found that relying on the leaderboard as an indication of the final position can be misplaced trust.

If you followed the competition forum, you will see team VSU also had multiple accounts for the same person, and they seem to have also fallen into the same trap of overfitting to the leaderboard - they ended up 9th on the 70% when they were first on the 30%.

The data mining lesson here is that you need to take all necessary steps to avoid overfitting, rather than just relying on the leaderboard feedback.

Congratulations to Nathaniel, Eu Jin (small world - I used to work with Nathaniel at the National Australia Bank and regularly see Eu Jin at the Melbourne R user group) and Alec, who clearly did not overfit. A Perfect Storm!

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