(MONEY Magazine) – John Allen Paulos is a math professor at Temple University and author of the best-selling Innumeracy. His forthcoming book is A Mathematician Plays the Stock Market.

Q. What can mathematics tell us about the stock market?

A. The market is the world's largest playground for numbers. And math can find patterns where they exist--or say that there aren't any where they don't.

Q. For example, you note that companies often do poorly after being featured on magazine covers. Is it the financial equivalent of the Sports Illustrated cover jinx?

A. The so-called jinx is the result of regression to the mean. You're on the cover because you've had a great year. But the nature of great performances is that they tend to be followed by average ones.

Q. You argue that efficient market theory is based on a paradox. What do you mean?

A. It's true to the extent that it's disbelieved--because only then are people angling for every little advantage. It's a very self-referential kind of tango.

Q. You lost money on WorldCom. What did you learn?

A. Don't put all your money on one stock no matter how sold you are on it. I don't think of myself as a victim, just momentarily stupid. --DAVID FUTRELLE