## NC State News

When the Wolfpack men’s basketball team became highly ranked in the Associated Press’s pre-season ranking, supporters were delighted. Sports rankings add to the prestige of a university’s athletics program and help determine which schools play in post-season games.

But what does being ranked No. 6 or No. 1 in the nation for chess, football or tennis actually mean? Are these subjective opinions or are science and mathematics involved? These questions are tackled by mathematics professor Carl D. Meyer and alumna Amy N. Langville, in their new book; “Who’s #1? : The Science of Rating and Ranking.”

The book, published by Princeton University Press this summer, explains how scientific ratings and ranking methods are created and applied. This is a follow-up to Langville and Meyer’s best-selling book,“Google’s Page Rank and Beyond: The Science of Search Engine Rankings,” published in 2006.

“Rating and ranking pops up everywhere –businesses, people, books, sports teams, and even universities care about being ranked in the top 10 or 20,” Meyer says.

Ratings and rankings are often contentious, Meyer says, especially with sports teams.

“Ratings and rankings have a huge effect.”

#### The Inspiration

Langville earned her doctorate at NC State and was inspired to write “Who’s #1?” when teaching her mathematics students the methods of the ranking systems for March Madness.

“The research became chapters then the chapters gradually became a book,” she says.

In “Who’s #1?” each chapter outlines a mathematical method at work. Chapter 3 features a method invented by Wesley Colley, an astrophysicist whose new method for ranking sports teams became so successful that it was incorporated in the BCS collegiate football ranking system.

Chapter 4 highlights a method invented by James P. Keener which stipulates a team’s strength should be measured by how well it performs against opponents but is tempered by the strength of those opponents. So, winning 10 games against weak competition shouldn’t be considered the same as winning 10 games against powerful opponents, the authors write.

Reviewers from TV stations, radio networks and prestigious mathematical publications such as the Society for Industrial and Applied Mathematics Review, a peer-reviewed journal, give “Who’s #1?” the thumbs up. Meyer is thrilled and contends the book opens the door to an entire world of exciting new possibilities.

“Often you have a lot of statistics about a team’s past performance, but how do you wrap it all up? These methods teach you that.”

- Photos by Marc Hall and Becky Kirkland.

### One response on “Who’s Number One?”

1. Alison Macdonald says:

I really enjoyed the earlier Google book and being a bit of a statistics geek look forward to Number One.

One thing I’ve been wondering is how things have now changed in ranking methods across the board given the massive quantities of data available online, especially given the huge uptake of microdata and microformatting using the schema org markup.

With countless millions of review websites using this format, it should be easy to harvest this data with simple bots – and I expect it must be a rich vein of statistical data.

Finally I guess the question must be asked – what number do you think the book will get to on Amazon?