View full lesson: http://ed.ted.com/lessons/check-your-intuition-the-birthday-problem-david-knuffke Imagine a group of people. How big do you think the group would have to be before there’s more than a 50% chance that two people in the group have the same birthday? The answer is … probably lower than you think. David Knuffke explains how the birthday problem exposes our often-poor intuition when it comes to probability. Lesson by David Knuffke, animation by TED-Ed.