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Want To Play A Statistics Game? (list the date of your b-day)

Discussion in 'BlackHat Lounge' started by BreaknBrix, Feb 1, 2015.

  1. BreaknBrix

    BreaknBrix Power Member

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    I saw this crazy shit on tv that I can't make sense of but it seemed real as hell and apparently there is math to back it up. I've always been real bad at math and want to see if this works and if so I need to know HOW.

    If you want to play, these are the rules:

    1) You need to list your b-day EXCLUDING the year. There is no need for the year.

    2) Make a decision after you read this line, that you are either going to play or you are NOT going to play. I must repeat. If you want to play just list the month and year. Don't tell yourself, "I'm not gonna play", then you read the responses, see a matching date and change your mind to "force" a math. You're either in or your out so make up your mind right now so we can avoid any sampling or confirmation bias.

    3) You should have your made up mind by now. Do NOT change it.

    Now this is how it's suppose to work.

    There are 365 days in a year. But apparently, if 30 people list their b-days (without the year) there's a >>70% chance we will see a match. So we have more than a 70% chance of getting a match before we get to page 2.

    On tv they only had to ask 10 people to get matching dates. I want to see if we can also get a match under 30. And if we do I'd like some math wiz to explain why there's a 70% chance of a match with 30 dates when there are still 335 dates left in the year.

    But let's place the game first! (if mods approve of course)

    I'll start: 6-28

    :)
     
  2. givensia

    givensia Regular Member

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    Assuming this is US format in terms of the date. 11-5.
     
  3. gb

    gb Regular Member

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    In US form : 11 / 17
     
  4. allison22

    allison22 Junior Member

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    I'm in, why not. 7/7
     
  5. Izzma

    Izzma Regular Member

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    Lets see where this goes BB,

    3-28

    (Assuming it is month/date)
     
    Last edited: Feb 1, 2015
  6. Haspel

    Haspel Power Member

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    ok im in

    6-3

    US format
     
  7. LostConnection

    LostConnection Senior Member

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    9/27 (US format I see)
     
  8. YouTubez

    YouTubez Regular Member

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    12-7

    Let's see how this goes.
     
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  9. Zwielicht

    Zwielicht Moderator Staff Member Moderator Jr. VIP

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    3/23 (month/date).

    I'll try to explain it after I see we get a match, although for now I'm going to assume it has something to do with the months that have the most births.

    Edit: It looks like zagard already beat me to it.
     
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    Last edited: Feb 1, 2015
  10. lord1027

    lord1027 Elite Member

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    I'll stick with US format too (for you guys, personally I hate it :D )

    15 - 08
     
  11. PandaDomo

    PandaDomo Senior Member

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    Why not :p

    2/8 (February 8th)
     
  12. _clicking_

    _clicking_ Power Member

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    12-7..December 7th
     
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  13. SimpleSiteSolutions

    SimpleSiteSolutions Jr. VIP Jr. VIP

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    US format is M/D

    9/8 (Sept 8th) is mine
     
  14. zagard

    zagard Jr. VIP Jr. VIP

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    January 16th

    But the number is right anyway, the chance quite high for us to find a match with 30 samples. Its simple, the first person has 365/365 chance to have unique date, for the second person its only 364/365 .. like that the 15th will only have 351 unique dates left with 15/365 = 4.1% chance to draw matching date, for the 30th its 8.2% chance to draw matching date
     
  15. PandaDomo

    PandaDomo Senior Member

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    Well, looks like it took 11 posts to get here :p
     
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  16. Hawkster

    Hawkster Jr. VIP Jr. VIP

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  17. reoman

    reoman Junior Member

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    12/25

    christmas day
     
  18. BreaknBrix

    BreaknBrix Power Member

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    Nice job man I didn't even notice that! :)

    11 freaking posts it took!

    That's 1 more than it took on tv and I'm still confused as hell. This doesn't make any sense at all. Let me get to this next post...


    Thanks a lot for trying to explain but your post just made me more confused.

    You're saying "8.2%" chance of drawing at 30 which is incredibly low.

    On TV they said it's a 70% chance.

    What am I missing here? I will do the same math you did.

    There are 365 days in a year. So the 2nd person who draws would have a 1/365 (1 divide by 365 X 100) or .27% chance of matching.

    The 2nd person would have a 2/365 or .8% chance of drawing.

    The 10th person would have a 10/365 or 2.7% chance

    The 30th would have a 30/365 or 8.2% chance (like you said).

    However, on tv they said that's not how the formula works. And they didn't bother to explain it cause they said most people wouldn't understand it. If the chance to draw at 30 is 8.2% that's incorrect based on the 70% figure I heard. So again, are there any mathematicians who know where that 70% chance is coming from?

    This is confusing the shit out of me cause I've seen it done twice the 1st time it took 10 samples to match the 2nd it took 11.

    THIS IS CRAZINESS.
     
    Last edited: Feb 1, 2015
  19. zagard

    zagard Jr. VIP Jr. VIP

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    Yes 8% is a freaking low chance if u only have 1 shot, but u see the 15th person gt like 4% chance to hit same date and from then on the chance will only improve and theres 15 more shots left.

    4% is like a guaranteed hit out of 25 shots, and close to 60% at 15 shots. while its true the 30th person only got 8% chance to hit same number, the 29th person will have 8% ish too. its like 8.2% 7.9% 7.6% 7.3% 7% 6.7% 6.4% 6.1% for the last 8 shots, this last 8 alone gv u nearly 57.2% chance to hit the matching date.
     
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    Last edited: Feb 1, 2015
  20. spectrejoe

    spectrejoe Jr. VIP Jr. VIP

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    27-12 (day 27 of december)