Answered => “Is there a plugin that makes the A/B testing of two WordPress themes possible?” on Quora.

http://www.quora.com/WordPress-Themes/Is-there-a-plugin-that-makes-the-A-B-testing-of-two-Wordpress-theme-possible

=> My answer…

Honestly, (if the designs are different enough) I think you might be asking for (visitor) trouble. If they visit on multiple browsers / devices – and they will – and get flip flopped across visits – which is what is going to happen even if you keep the theme per visit / cookie steady – then you’re really not going to get an accurate read anyway. That is, the flipping flopping effect is going to effect usability, etc. In other words, your sampling is going to compromise your sample, so to speak.

That said, you might be able to get away with a week to week “trial”. Or do some sort of requesting IP redirection so (for example) west of the Mississippi gets one theme and east of gets the other. Maybe by browsers? Too?

Perhaps I’m jumping to too fast of a conclusion but simple putting A/B in play at the WordPress theme level doesn’t sound like the optimal approach to me.