Matt's blog

September 26, 2009

The study methodology: sort of like the Netflix Prize

How do researchers determine what ties folks to their community? Turns out it's sort of like how Netflix determines what draws you to different movies.

If you haven't heard of the Netflix Prize, here's a quick synopsis: Netflix, the movie rental company, promised $1 million to any team of statistical wizards that could improve the accuracy of the company's legendary recommendation engine by 10 percent. When I first heard about this prize, I wondered, "Given that movie tastes are so subjective, how could they quantify exactly how accurate their system was?"

The answer is ratings. Netflix users have given the company hundreds of millions of ratings for lots and lots of movies. Netflix knows it's improved the recommendation engine when it can better predict how you'll rate a particular movie. So to test the teams who entered the contest, Netflix gave them access to a partial set of movie ratings by Netflix users. The company held onto another set of ratings by the same users, and the teams competed to see who could best predict what those other ratings would be. To figure out what rating a user might give to a certain movie, the teams had to look for obscure patterns in other ratings the user had given, and try to figure out which of those patterns were most important to the user's overall taste.

To determine the factors that drive a person's loyalty to and passion for her area, Gallup researchers used a similar solution. First, they identified the attachment factor — how strongly a person was tied to her place. Then, they considered the ratings residents gave to different aspects of their communities — things like health care services, housing affordability, and entertainment venues. From those ratings, the team looked for patterns that would best predict the attachment factor.

It turns out that for most communities, researchers need only three ratings — social offerings, openness and aesthetics — to predict much of a person's attachment.

Image courtesy of billaday on Flickr.


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