Patrick Deglon worked at CERN from 1996-2002 where he analyzed particle collision data from experiments. He used large-scale computational analysis and statistics to make discoveries about particle properties and interactions. In 2004, he joined eBay where he now leads analytics to understand customer behavior and measure the impact of initiatives using A/B testing and other techniques. He discusses how the challenges of analyzing large datasets at CERN prepared him for working with eBay's "big data".