Same Date Birthdays

[aimee]

If you have 50 people in a room, what are the chances that at least 2 of them with share a birthday. It's not as easy as it sounds - it would be 50 into 365 only if the date was specified.

[Bob...]

1 in 25

[sylvday]

There only need to be about 23 people in the same room for the chances to be even that two of them will share the same (non specified) birthday. For proof of this see http://www.people.virginia.edu/~rjh9u/birthday.htm
l The graph on this website seems to indicate that with 50 people in the room, the chances are in excess of 10 to 1 ON two of them sharing a birthday. In other words, you'd be stupid to bet against two of them sharing a birthday.

[jenstar]

Ah... the classic version of this puzzle is "how many people need to be in a room for there to be a 50% chance that two of them share the same birthday?", to which the answer is 23. So obviously with 50 people in a room, the chance is going to be much higher. The formula for calculating it is 1-(364/365 x 363/365 x 362/365 x 361/365 etc...) until you get down to 365-(n-1)/365 where n is the number of people in the room.

[Insane Wally]

Two of my cousins share the same birthday & there's 3 years between them (they are brothers), what's the odds on that one?

[nona suomy]

I share my birthday with everyone that knows me. It's mine but I share anyway... I'm good like that.

[coggles]

Insane Wally, both our children (not mine and yours, mine and my husbands!) were born on the same day 3 years apart. I recently bumped into a lady I hadn't seen for a couple of years. We used to go to the same Mum & baby group. She had another child by then too - born on the same day as her first, 3 years apart. We were absolutely flabbergasted!

[coemgen]

It isn't as unusual as it sounds. My eldest and 2nd youngest both share a birthday 8 yrs apart, also my husband and his sister share a birthday 1 yr apart.

[IndieSinger]

But surely the chance of your own children sharing a birthday isn't that great, because you just make sure you... y'know... at the same time of year? The chances are surely then greatly reduced?

[coemgen]

Not at all. We never planned any of our kids, they just happened. Even if we had tried to plan, there's no guarantee it will work is there?

[Greedyfly]

lets test the theory: mine is 1/7/83

[bernardo]

About 98%

[coggles]

IndieSinger, I had to have fertility drugs to conceive both our children (and one I lost in between) so as much as mr coggles and me were at it like rabbits, we were very lucky to have children at all, let alone try and have them on the same day!