CHRISTIAN CALDERON, CRO of Ketchapp: "In the performance business especially, marketing is math. If the numbers aren’t working out, it’s usually an indicator something is wrong. The first place where you see it is the funnel metrics, like click-through and conversion rate. You look at pre-install KPIs, and if you see something abnormal you’ll have a sense of if it’s fraudulent. Is the yield off here? Understand the math behind your user acquisition. That lets you know if something unusual is happening, and if you can detect fraud that early, sometimes you can get your money back depending on who you’re working with."