Birthday Paradox
How large a group needs a shared birthday? Change the group size and experiment.
With 23 people, the chance of a shared birthday is 50.7%
Birthdays in this group (month / day)
All birthdays are different this time.
Matches in 0 of 1 groups. Observed 0.0%; theory 50.7%.
Each birthday is independent and equally likely on any of 365 days. Leap years and seasonal variation are excluded. Dates use month/day format.
How to play
Change the group size to move the dot along the curve. Try once to gather a new group. Outlined calendar dots mark shared birthdays. Run 1,000 groups to compare the observed frequency with theory. Changing group size resets the results.
Learn more
Each birthday is independent and equally likely on any of 365 days. Leap years and seasonal variation are excluded. Dates use month/day format.