It is surprising (but true) that if 23 people are in the same room, there is about a 50% chance that at least two people will have the same birthday. Suppose you want to estimate the probability that if 30 people are in the same room, at least two of them will have the same birthday. You can proceed as follows.

a. Generate the birthdays of 30 different people.
Ignoring the possibility of a leap year, each person has a 1
365 chance of having a given birthday (call the days of the year 1, 2, . . . , 365). You can use a formula involving the RANDBETWEEN function to generate birthdays.

b. After you have generated 30 people’s birthdays, how can you tell whether at least two people have the same birthday? The key here is to use Excel’s RANK function. (You can learn how to use this function with Excel’s online help.) This function returns the rank of a number relative to a given group of numbers. In the case of a tie, two numbers are given the same rank. For example, if the set of numbers is 4, 3, 2, 5, the RANK function will return 2, 3, 4,