OT: Experiment, please give your input...

[raj]

Another 2 day miss.  Mine's October 13

[ulthar]

I've met two people with the same birthday (one was even the same year...we were born only hours apart in different towns) as me and a BUNCH within one or two days....as common as it must be statistically, I still find it fascinating.

[Will]

April 25th, same as Al Pacino.  My cousin has the same birthday as I, only one year later. My sister's birthday is the same as another cousin's.  A really bad birthday-based b-movie is Happy Birthday to Me.

[dean]

me, may 23, I also play basketball with the a guy with the exact same birthday as well, but i think i am like 12 hours older than him, still i think it's pretty cool though.

i also know someone on 12 november neon, does that mean i win a prize?

:-P

[Bernie]

August 26

[Velvet Brotha]

July 12th... hmmmm... so much for that statistic. ; )

[Vermin Boy]

October 26. Same day as Hilary Clinton, Pat Sajak, Leon Trotsky, and Jackie "Uncle Fester" Coogan.

[The Burgomaster]

April 11.

The 99.9% chance seems to makes sense based on the following:

Say you had only 4 people, numbered 1, 2, 3, and 4.  You would have the following combinations:

1 could have the same birthday as 2
1 could have the same birthday as 3
1 could have the same birthday as 4
2 could have the same birthday as 3
2 could have the same birthday as 4
3 could have the same birthday as 4

This gives 6 possible matches with only 4 people.  Below, I have laid it out more visually:

(1,2) (1,3) (1,4)
(2,3) (2,4)
(3,4)

The top row has 1 fewer combination than the number of people involved (4 people involved minus 1 = 3 combinations in the top row).  Each row below it decreases by 1 combination (top row has 3, middle row has 2, bottom row has 1).

If you extend this out to a population of 30 people, you will get the following:

29 + 28 + 27 + 26 + 25 . . . .all the way down to 1.  If you add this up it comes to 435 possible matches for a group of 30 people.  

I have no idea what the statistical formula would be to figure all this out (and I'm too lazy to look it up in my statistics book, which is about 10 feet away), but it seems like there are a lot of possible matches among 30 people.

[Kory]

7 July

[Susan]

fwiw - march 10

There sure are quite alot of april b-days. i bet nobody shares mine, i've never met anyone with my birthday. And in my job i see the birthdates of every person i set up for insurance and haven't seen anyone with my birthday.

I share birthday with Osama Bin Laden, James Earl Ray and Chuck Norris.

woo hoo

[Neon Noodle]

I met someone at my job who has the same birthday as me - and it was while someone was discussing this statistical odditity - perhaps someone is tapping badmovies.org? the horror!

[Mofo Rising]

August 10

Solution to the Birthday Problem

Looks like The Burgomaster was on the right track, even if the original statistician wasn't completely correct with his 99.99% prediction.  At 30 people it's about a 70.63% chance.  If you have a good calculator that page will show you how to do all the calculations yourself.

So, it would seem that to be absolutely sure you get two people who share the same birthday the actual number would have to be 367.  Right?

Any doubles yet?  Anybody keeping track?

[jmc]

July 31.

The prof ran this experiment in a math class I had once...only took ten tries to find a match.

My father and my father-in-law were both born on March 18.

[Flangepart]

January 12th.

[daveblackeye15]

My brother's birthday is June 23.