Chapter 15: Chances, Probability, and Odds: Measuring Uncertainty
Internet Excursions


It's Your Birthday!

Suppose there are 35 people in the room. What do you think the probability is that at least two people share the same birthday? The answer to such a question is not necessarily obvious. It would seem that the probability would be fairly small. One way to get an idea is to take a survey of groups of thirty-five. Another way would be to run a simulation . (We will assume an equal likelihood of each birthday and not include February 29.)

1.  

Run the simulation ten times for 35 people and tabulate the results. What is the experimental probability based on the simulation?

2.  

Repeat the simulation for groups of 20, 25, 40, 45, and 50 people. Does the probability appear to increase rapidly or slowly?

3.  

Compute the theoretical probability directly using a graphing calculator or computer. (Hint: Compute the probability that no one has the same birthday.)

4.  

The simulation randomly generates one of 365 days for each person. How might you take into account a person born on February 29?

5.  

How would you use the simulation to estimate the probability that no one has the same birthday as you?


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