Complicating Birthday Statistics

It may be surprising that only a small group of people is needed in order to result in what is known as a birthday paradox, or coincidence. That is when two people within a group celebrate the same date of birth. Most people think that there would need to be a rather large group in order for this to happen, yet that is not the case.

When you add a third person to the group they have only 363 days to miss having the same birthdays as the first two people. Meaning they have a probability of 363/365, or 0.9945 and when you multiply this to the previous results it results in a 0.9918 chance of them having the same birthday. The probability results of 0.0164 (1-0.9836) of having matching birthdays is the result when you add a fourth person to the group.

Even though it may be interesting to learn different facts and discover unusual tidbits about ordinary events or processes, most people would probably prefer to celebrate the uniqueness of certain celebrations such as a birthday, with the exception of multiple births. It is a unique, special event for one special person on one special day.

They prefer to celebrate in the more traditional way of throwing a birthday bash, complete with presents, cards, some party favors and a birthday cake. They also prefer to leave all of the analytical aspects, such as equations, percentages and probabilities to those who are less sentimental.

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