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Check your intuition: The birthday problem - David Knuffke

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  • 12,383 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.


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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 Labovic
  • 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
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!


Customize this lesson

Create and share a new lesson based on this one.

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 Labovic
  • 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

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