The birthday paradox, hard to believe

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hooknife
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Registered: Apr 2003
Location: Inside Layer 3

The birthday paradox, hard to believe

The birthday paradox states that if there are 23 people in a room then there is a slightly more than 50:50 chance that at least two of them will have the same birthday. This means that a higher probability applies to a typical school class size of thirty, where the 'paradox' is often cited. For 60 or more people, the probability is greater than 99%. This is not a paradox in the sense of leading to a logical contradiction; it is a paradox in the sense that it is a mathematical truth that contradicts common intuition. Most people estimate that the chance is much lower than 50:50. Calculating this probability (and related ones) is the birthday problem. The mathematics behind it has been used to devise a well-known cryptographical attack named the birthday attack.

Taken from - http://en.wikipedia.org/wiki/Birthday_paradox

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Jun-28-2005 14:49 United States

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Fundamental
Still Alive in '25

Registered: Apr 2001
Location: Scotland

Re: The birthday paradox, hard to believe

I made some money off of this once. I made a bet for £20 with a friend that I could find 2 people at this house party with the same birthday. There was about 40 people there so I knew I had the odds in my favour.

I found 2 sets of 2, didn't get paid twice though...

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Jun-28-2005 15:13 Scotland

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hooknife
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Registered: Apr 2003
Location: Inside Layer 3

Re: Re: The birthday paradox, hard to believe

quote:
Originally posted by Fundamental
I made some money off of this once. I made a bet for £20 with a friend that I could find 2 people at this house party with the same birthday. There was about 40 people there so I knew I had the odds in my favour.

I found 2 sets of 2, didn't get paid twice though...

hmmmmmm......thats a damn good idea, I'll have to try that one.

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Jun-28-2005 15:37 United States

jonze
Unicorn Farts

Registered: Feb 2004
Location: where blue skies meet the sunrise

statistics professors love to do that in their classes.

Jun-28-2005 15:42

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M@t
Senior tranceaddict

Registered: Dec 2003
Location: Newcastle

bumpety click

for research's sake

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Jun-28-2005 17:00 England

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Inertia
yes.

Registered: Jul 2002
Location: Santo Domingo, Dominican Republic

i do find that hard to believe. in a school of 400+, i'm the only one with my birthday.

the only other people i know of with my same bday (feb 12) are abe lincoln, this dude i recently met, and the mother of one of my friends.

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Jun-28-2005 17:42 Dominican Republic

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hooknife
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Registered: Apr 2003
Location: Inside Layer 3

quote:
Originally posted by Inertia
i do find that hard to believe. in a school of 400+, i'm the only one with my birthday.

That is not the normal, obviously.

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Jun-28-2005 18:02 United States

Resnick
Supreme tranceaddict

Registered: Feb 2003
Location: Toronto

quote:
Originally posted by hooknife
That is not the normal, obviously.

actually it is...theres a difference between someone having ur birthday and any 2 ppl having the same birthday

statistically tehre should be 1 other person in ur school that has ur bday (in 400 ppl)

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Jun-28-2005 19:52 Canada