FYI, this is a really amazing article about A/B split testing.
Magento has built-in functionality for using Google’s Website Optimizer to do A/B split tests automatically (it uses javascript to show a different category header for one person vs. the next, and then tracks which one is most effective).
The A/B Test: Inside the Technology That’s Changing the Rules of Business
http://www.wired.com/wiredenterprise/2012/04/ff_abtesting
Thanks,
Jeff