Re: [Harp-L] on the matter of shared birthdays

["John Kerkhoven" <solo_danswer@xxxxxxxxxxxx>]

A burning issue, I know....

There is a brief discussion of the probabilities of birthday sharing on
pages 142-143 of the Life Science Library (1963) book on Mathematics.

The probability of two people in a group sharing the same birthday increases
with the number of people in the group. Above 50, the likelihood is almost
certain.

How so?

In a given group, there are only so many ways their birthdays can be
distributed throughout the year. Everybody born on January 1; everybody but
one born on January 1, and the other person on January 2. And so on. You
take the total number of possible times that at least two people share a
birthday divided by the total number of possible distributions of birthdays,
and you get the probability for that particular size of group.

No one said it had to be intuitive.

I'm sure everyone can sleep better now.

Harmonica content:

What is the likelihood that at a SPAH jam, two harmonica players will have
exactly the same brands and keys of harmonicas?

(Okay, a whole different statistical kettle of harps, but I had to get
something in.)

John