You hear that a rare disease test is 99% accurate, and your friend tests positive. You panic and think they must be very sick. But what if only 1 in 10,000 people actually have it? Suddenly, it's less likely they’re ill—even with that positive result. Or imagine seeing a sports player score a goal in their first game. You think they’re amazing, but forget that most players fail often. Take the quiz to find out what’s really going on here.