Lesson: Birthday Problem

What is the probability that in a room of 25 people at least 2 people share the same birthday? What is your guess? Use the simulation below to empirically (by experiment) figure out the probability.

Use: https://spholmes.shinyapps.io/birthday_app/
After you open the link above:

Run the simulation for 25 people 10 times. Record the number of times you had at least one match for each trial. What is the percentage of successful matches to trials? (One or more matches counts as only one match.)

Student activity and collective crowd sourcing

Have students collect the birthday data on several groups of 25 people. These people can be arbitrarily chosen as long as you do not pay any attention to their birthdays until you have the 25 people chosen. For example you can choose the first 25 presidents of the United States or any 25 from a current list of presidents.

See actual probabilities - download the Excel file. Make a comparable graph comparing your results to the actual probability graph. See example on the teacher page.)

Source: Original Version 1.0 developed at CIESE-
Center for Innovation in Engineering & Science Education (2007)
Revised 10.24.19 currently under construction