[srom]

Indeed Google Analytics has added the multi-armed bandit approach in Content Experiment. It's quite slick btw, but definitely more difficult to implement than traditional split testing. My 2 cents:

[1] the sample size calculator (How many subjects are needed for an A/B test?): http://www.evanmiller.org/ab-testing/sample-size.html

[2] <unashamed plug> easyAB: a jquery plugin for easily start A/B testing using Google Analytics. http://srom.github.io/easyAB/ </plug>