Skip to main content

TED-Ed

Check your intuition: The birthday problem - David Knuffke

2,959,536 Views

14,254 Questions Answered

TEDEd Animation

Let’s Begin…

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.

Additional Resources for you to Explore

The actual origin of the birthday problem is not clear, however it was featured in the April 1957 edition of "Mathematical Games" in Scientific American, a long running series of mathematical puzzles that was authored by noted math/science popularizer Martin Gardner. There are many different presentations of the Birthday problem. Here’s an interactive model that allows you to determine the probability of a birthday match for different sized groups of people.

The Khan Academy has a video lesson on this problem. Visit this NPR link: Math Guy: The Birthday Problem for one last review!


About TED-Ed Animations

TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

Educator
David Knuffke
Director
Biljana Labović
Script Editor
Eleanor Nelsen
Animator
Kaitlyn Carroll
Sound Designer
Weston Fonger
Associate Producer
Jessica Ruby
Content Producer
Gerta Xhelo
Editorial Producer
Alex Rosenthal
Narrator
Addison Anderson

More from Math In Real Life