Soccerdude2's claim is, in theory, correct if we were to assume that each of the 365 days in a year (February 29 not included) had an equal number of birthdays of the people in this world. Other than that, it has nothing to do with statistics. It is a matter of probability.

The fact remains that your % chance of someone sharing a birthday with someone else in the room, assuming it is truly random, is 23/365, which is 6.3%.

No. I'm not sure how you came up with this, but this is not true.

To determine the probability in which no one in a room of 23 shares a birthday, let us consider each person separately and in order. Allow Person 1 to have any birthday (365/365). Now the probability for Person 2 to not share a birthday with Person 1 is (364/365). Similarly, the probability for Person 3 to not share a birthday with the former two is (363/365). Continue on and you get to Person 23 with 343/365. If we were to multiply this out, we would receive the probability in which no one shares a birthday, which equates to roughly 49.3%. Subtract from 1 (1 - .493), and we have 50.7%, the probability in which two or more people share a birthday in a room of 23 people.

If we were to multiply this out, we would receive the probability in which no one shares a birthday, which equates to roughly 49.3%. Subtract from 1 (1 - .493), and we have 50.7%, the probability in which two or more people share a birthday in a room of 23 people.

Followed you up to here, and now I have absolutely no clue where you get 49.3%. 343/365 = .94 approximately, which means there's a 94% chance of not sharing a birthday, OR, conversely, a 6% chance of sharing...which is what I said earlier.

So yeah. Please elaborate on how you got 49.3% and 50.7%.

Followed you up to here, and now I have absolutely no clue where you get 49.3%. 343/365 = .94 approximately, which means there's a 94% chance of not sharing a birthday, OR, conversely, a 6% chance of sharing...which is what I said earlier.

Sorry, I wasn't too clear. What I meant by "multiply this out" was this:

(1/365)^23 * (365*364*363...343) = .493
rnHere's the calculation on WolframAlpha to save you some time. (Hopefully it shows up.)

Should there ever be any doubt in my claims?

Basically Kasic like rayoflight3 said you take the chance of someone not sharing a birthday with someone else (364/365) and then someone else not sharing a birthday with both of them (363/365) and so on (362/365)(361/365)(360/365)(359/365)...(343/365) and multiply them together to get the total chance of 23 people not sharing a birthday (49.3%). Subtract that from one and you get the opposite, the chance that someone shares a birthday with someone else in that room of 23 (50.7%).

The key is thinking of any person out of the 23 sharing a birthday with any other person out of the 23.

Blackbeltr0: epiphany January 6

Found this thread thanks to 70_70_70

My birthday was on October 5, 1999.

Ernie15 - 1/5/1982
      Blackbeltr0: - 1/6/????
IAgreeWithYou - 1/16/1998
            Skeleton_Pilot - 1/18/1987
                      jeol - 1/23/1996
        GhostOfHorror - 1/24/1999
                 Clancy12 - 1/25/1999
Gamecholic - 1/29/1994
                  xeano321 - 2/14/1996
                   zakyman - 2/14/1997
                Star_shine - 2/24/1999
ShadowArchon - 2/27/1998
                   Salvidian - 2/29/1996
            Max000_Extreme - 3/20/1999
                    Pedro97 - 3/21/1997
                      1zth - 3/22/1999
                       cje95 - 3/25/1995
          ironblade41 - 4/1/1999
               pangtongshu - 4/3/1995
                 Sauron23 - 4/10/1999
                   wflag10 - 4/14/1999
                  BRAAINZz - 4/19/1997
        NoobSlayer3000 - 4/29/1997
IAgreeWithYou - 4/31/1998
killersup10 - 5/2/1999
                nichodemus - 5/7/1994
       Jefferysinspiration - 5/9/1991
                     Drink - 5/10/1994
              ChillzMaster - 5/13/95
awesomeplayer312 - 5/14/1999
    70_70_70 - 5/15/1991
               psychoraven - 5/21/1998
            Redslaughterer - 6/4/1999
                Darkfire45 - 6/11/1996
                partydevil - 6/17/1976
        EmperorPalpatine - 6/20/1993
             thebluerabbit - 6/21/1993
      Kasic - 6/30/1993
                  Alpha791 - 7/2/1998
              Alexandra222 - 7/3/1996
                    daleks - 7/6/1995
                   Kyouzou - 7/16/1994
            MachineofLight - 7/17/1999
                  R2D21999 - 7/23/1999
   feedback123 - 8/2/1990
                  MrDayCee - 8/5/1976
             GhostOfMatrix - 8/10/1995
                      jezz - 8/19/1993
               superdark33 - 8/30/1994
                  goumas13 - 9/7/1992
superbobdabest/superbob111 - 9/11/1999
               soccerdude2 - 9/19/1997
        StormWalker - 9/19/1998
            AatosLiukkonen - 9/23/1996
                  Jeff1999 - 9/24/1999
               BritHennerz - 9/24/1995
                    toemas - 9/26/1998
                pickpocket - 10/1/??? (unknown millennium)
              Skulltivator - 10/1/1992
SaifureRahma - 10/5/1999
                       fireangle - 10/6/1999
     walshymusic - 10/18/1995
                    _Spaz_ - 10/21/1994
              skydragon720 - 10/30/1998
               mattzor - 10/30/1997
         ImTheMostManlyMan - 10/31/1998
             Tactical_Fish - 11/21/1996
                Minotaur55 - 11/26/1997
                    xAyjAy - 11/27/1989
                Gamer_Cale - 11/30/1994
               alexandrica - 12/5/1999
         Osumnis - 12/7/1997
                     dair5 - 12/18/1996
                idigit - 12/21/1998
                    Armpit - 12/25/1980
                   Jacen96 - 12/27/1996

BlackBelt, please provide a year otherwise you will be deemed elderly.

Here's an updated list doing what I should have done long ago, removing the innactive/banned. If you have been removed and would like that to change then just say so.

      Blackbeltr0: - 1/6/????
IAgreeWithYou - 1/16/1998
            Skeleton_Pilot - 1/18/1987
                      jeol - 1/23/1996
        GhostOfHorror - 1/24/1999
                 Clancy12 - 1/25/1999
Gamecholic - 1/29/1994
                  xeano321 - 2/14/1996
                   zakyman - 2/14/1997
                   Salvidian - 2/29/1996
            Max000_Extreme - 3/20/1999
                    Pedro97 - 3/21/1997
          ironblade41 - 4/1/1999
               pangtongshu - 4/3/1995
                 Sauron23 - 4/10/1999
IAgreeWithYou - 4/31/1998
killersup10 - 5/2/1999
                nichodemus - 5/7/1994
       Jefferysinspiration - 5/9/1991
              ChillzMaster - 5/13/95
awesomeplayer312 - 5/14/1999
    70_70_70 - 5/15/1991
            Redslaughterer - 6/4/1999
                partydevil - 6/17/1976
        EmperorPalpatine - 6/20/1993
             thebluerabbit - 6/21/1993
      Kasic - 6/30/1993
              Alexandra222 - 7/3/1996
                   Kyouzou - 7/16/1994
            MachineofLight - 7/17/1999
                  R2D21999 - 7/23/1999
   feedback123 - 8/2/1990
                  MrDayCee - 8/5/1976
             GhostOfMatrix - 8/10/1995
                      jezz - 8/19/1993
                  goumas13 - 9/7/1992
superbobdabest - 9/11/1999
               soccerdude2 - 9/19/1997
        StormWalker - 9/19/1998
                  Jeff1999 - 9/24/1999
                    toemas - 9/26/1998
                pickpocket - 10/1/??? (unknown millennium)
                       fireangle - 10/6/1999
     walshymusic - 10/18/1995
              skydragon720 - 10/30/1998
               mattzor - 10/30/1997
         ImTheMostManlyMan - 10/31/1998
             Tactical_Fish - 11/21/1996
                Minotaur55 - 11/26/1997
                    xAyjAy - 11/27/1989
                Gamer_Cale - 11/30/1994
               alexandrica - 12/5/1999
         Osumnis - 12/7/1997
                   Jacen96 - 12/27/1996

5/25 I DO NOT need you to know my age.

I shall not add you then, I'm fairly confident about other people being above the limit but I've not come in enough contact with you and you seem far too protective of your age so I shall not add.