A/B Testing is very important in any modern online application. Designers learn to trust metrics (rather than the HiPPOs – the Highest Paid Person's Opinions) in assessing the efficacy of new features. Testing provides a rational basis for evaluation of the feature variations, and can result in significant improvement in the performance of an application. This presentation will introduce techniques used in experimental design in engineering, bio-medical, pharmaceutical contexts and provide an overview of how these may be adapted for use in optimizing online games, employing statistics which provides us with the tools to determine a confidence in the results we observe. We will examine the infrastructure required to implement testing efficiently within a game production pipeline for mobile and online games. We'll also explore the challenges you'll face when implementing A/B Testing, and hopefully speed you on your way to creating a successful testing culture within your organization.