The birthday coincidence or paradox results when two people within a group share the same date of birth. Surprisingly, in order to have a fifty/fifty probability of sharing the same birthday, there is only a small group of people required, rather than the more expected thought of needing a large group.
The third person in the group, having to miss the birthdays of the first two people, has only 363 days, with a probability of 363/365, which is 0.9945. Multiplying this by the previous result will give 0.9918 chances of having the same birthday. For four people in the group, the probability of a pair of matching birthdays is 1-0.9836 = 0.0164, which is over 1%.
Although it can be interesting to take a topic and dissect it in this manner, most people do not look at birthdays in this type of analytical terms. Instead, it is considered to be a very special day for a very special person, or in the case of multiple births, very special people.
A birthday celebration complete with a birthday cake, birthday gifts and perhaps birthday flowers is the most traditional way that people celebrate someone’s birthday; leaving all of the probabilities, percentages and equations to those who prefer statistics over the more sentimental reasoning.
To read more The Birthday Celebrations
