Which ads work and how and why do they achieve their goals? The IAB Ad Effectiveness Council recently released its "Guide to Designing Digital Ad Impact Studies", and in the latest episode we discuss testing and measuring the impact of advertising with two of the guide's authors, Andy Ford, Head of Marketing Science, ANZ at Facebook and Mark Duffy, National Head of Product and Partnerships at Columbus, a Merkle Company. We run through setting up experiments, what to measure, which metrics to use (and not to use) and the role and value of creative.