birthday paradox

This is a discussion on birthday paradox within the A Brief History of Cprogramming.com forums, part of the Community Boards category; I am back because of an interesting thing called Birthday Paradox Let's see how many of us share a common ...

  1. #1
    Big & Little Wong Tin-Bar Jackie Chan's Avatar
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    birthday paradox

    I am back because of an interesting thing called Birthday Paradox

    Let's see how many of us share a common birthday.

    I will edit this post to add to the list, just post your replies in this format
    UserName MonthName DayOfMonth

    Code:
    1) Jackie Chan April 7
    2) Prelude Nov 11
    3) Neo1 October 11
    4) brewbuck February 7
    5) ahluka June 7
    6) ping December 15
    7) anon October 25
    8) indigo0086 June 13
    9) Mario F. August 23
    10) BMJ May 29
    11) maxorator March 25
    12) SlyMaelstrom August 10
    13) abh!shek January 10
    14) P4R4N01D 28 February
    15) QuantumPete 11th August
    Last edited by Jackie Chan; 06-13-2008 at 03:03 AM.

  2. #2
    Code Goddess Prelude's Avatar
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    Cboard has a calendar, you know. It's probably going to give you a better sample than a few people on a single thread.

    Prelude Nov 11
    My best code is written with the delete key.

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    Internet Superhero
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    Neo1 October 11
    How I need a drink, alcoholic in nature, after the heavy lectures involving quantum mechanics.

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    Captain Crash brewbuck's Avatar
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    brewbuck February 7

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    Supermassive black hole cboard_member's Avatar
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    ahluka June 7

    Officially depressed about turning 20
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

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    Registered User
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    ping December 15
    Code:
    >+++++++++[<++++++++>-]<.>+++++++[<++++>-]<+.+++++++..+++.[-]>++++++++[<++++>-] <.>+++++++++++[<++++++++>-]<-.--------.+++.------.--------.[-]>++++++++[<++++>- ]<+.[-]++++++++++.

  7. #7
    The larch
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    anon October 25

    We could probably get 365 replies before we find 2 people that have birthday on the same day (it would be great to disprove the paradox )
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  8. #8
    Ethernal Noob
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    June 13....

    I'm Serial.

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    (?<!re)tired Mario F.'s Avatar
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    Alas. The theory falls.

    August 23.
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  10. #10
    Captain Crash brewbuck's Avatar
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    Well, it doesn't help if a person with a matching birthday deliberately doesn't post theirs

  11. #11
    BMJ
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    BMJ May 29


  12. #12
    (?<!re)tired Mario F.'s Avatar
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    Quote Originally Posted by brewbuck View Post
    Well, it doesn't help if a person with a matching birthday deliberately doesn't post theirs
    That's the beauty of these probability theories; they explain nothing because they can't be disproven. Only proven. That is, they are true because that's just the nature of probabilities.

    Or better yet, for every set of results that disprove the theory, one can always argue a bigger set can prove it.

    I'm not sure why we should waste time on it
    The exact same theory can immediately be applied to people's height, weight, cars with the same two initial letters in their license plates, poking my nose at the same time as someone else...
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  13. #13
    Reverse Engineer maxorator's Avatar
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    "The Internet treats censorship as damage and routes around it." - John Gilmore

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    Registered User whiteflags's Avatar
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    That's the beauty of these probability theories; they explain nothing because they can't be disproven. Only proven. That is, they are true because that's just the nature of probabilities.
    I wouldn't say that the likelihood of an event occuring (even if in real world demonstration it is very unlikely because only a subset of humanity will ever produce an evenly distributed sample) makes the statement any less of a fact. You could simulate a number of assumptions by computer:

    Code:
    // Nobody in the sample was born on February 29
    // Everyone's birthdays in the sample are evenly distributed
    
    double bd_paradox (int n)
    {
        return n == 1 ? 1.0 : (365.0 - (n - 1)) / 365.0 * bd_paradox(n - 1);
    }
    
    #include <iostream>
    #include <ostream>
    #include <iomanip>
    int main ()
    {
        for ( int n = 1; n <= 365; n++ ) {
            std::cout << n << ": " << std::scientific << 1.0 - bd_paradox(n) << '\n';
        }
        return 0;
    }
    
    
    1: 0.000000e+000
    2: 2.739726e-003
    3: 8.204166e-003
    4: 1.635591e-002
    5: 2.713557e-002
    6: 4.046248e-002
    7: 5.623570e-002
    8: 7.433529e-002
    9: 9.462383e-002
    10: 1.169482e-001
    11: 1.411414e-001
    12: 1.670248e-001
    13: 1.944103e-001
    14: 2.231025e-001
    15: 2.529013e-001
    16: 2.836040e-001
    17: 3.150077e-001
    18: 3.469114e-001
    19: 3.791185e-001
    20: 4.114384e-001
    21: 4.436883e-001
    22: 4.756953e-001
    23: 5.072972e-001
    24: 5.383443e-001
    
    // and so on ...
    But it certainly has applications. The birthday paradox shows that even if the number of bins is much greater than the number of items, the probability that two items will randomly be put into the same bin is still very high. The lesson to be learned in relation to computer science is that efficient handling of the bins containing lots of items is always necessary.

  15. #15
    (?<!re)tired Mario F.'s Avatar
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    Hmm... interesting point.
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

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