Across medicine, business and government, there’s no simpler or more powerful tool for finding out what works than a randomised experiment. Investigating everything from jails to ad campaigns, philanthropy to schools, the randomistas are building evidence and busting myths. Randomised tests are carried out on us every day: by supermarkets, search engines, online dating sites and direct marketers. Political parties use randomised trials to win elections. But how do these tests work? Are there any ethical issues? And what do they reveal about our choices? In Randomistas, Andrew Leigh tells the stories of radical researchers who overturned conventional wisdom in medicine, politics, economics, law enforcement and more. From finding the cure to scurvy to discovering what policies really improve literacy rates, randomistas have shaped life as we know it – but they often had to fight to conduct their trials and have their findings implemented. In the tradition of Malcolm Gladwell, Randomistas is a brilliant and entertaining exploration of a hidden but vital foundation of modern life.