Choose a group of people, such as a classroom of students, a group of friends, or the members of a club. Count the number of people in the group and determine the probability that at least two of them were born in the same month.

Check several classes, or groups of people, of the same size. In how many of the groups do two people share the same birthday? Use the results to estimate the probability that two people in a group that size share the same birthday.