The Google Algorithm

1 Mar 2010

Wired’s Steven Levy on Google search:

Every time engineers want to test a tweak, they run the new algorithm on a tiny percentage of random users, letting the rest of the site’s searchers serve as a massive control group. There are so many changes to measure that Google has discarded the traditional scientific nostrum that only one experiment should be conducted at a time. “On most Google queries, you’re actually in multiple control or experimental groups simultaneously,” says search quality engineer Patrick Riley. Then he corrects himself. “Essentially,” he says, “all the queries are involved in some test.” In other words, just about every time you search on Google, you’re a lab rat.