He has been called “Stanford’s star of statistical inference,” and he is responsible for creating a swathe of modern statistics, including the bootstrap. But when Brad Efron first heard about a project to tackle the horrific prevalence of rape in Nairobi’s poorest schools, his first thought was that it required more than statistical help—it required “angelic” intervention. “I put it in the category of great ideas that couldn’t be carried out,” he says. “How do you actually execute a highly interactive interventional plan within a disparate public-school system—and then how do you show whether the interventions are working?”