Math Is Fun Forum

Hannibal lecter

Member

Registered: 2016-02-11

Posts: 392

why I can't calculate the probability of birthday problem without...

Hi, why I can't calculate the probability of birthday problem without taking the complement ?

for example why I can't calculate the probability of at least 2 shared birthday in a room of 30 people
without taking the complement ?

is it too hard? but how to do it?

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Wisdom is a tree which grows in the heart and fruits on the tongue

Alg Num Theory

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Registered: 2017-11-24

Posts: 693

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Re: why I can't calculate the probability of birthday problem without...

You can do it this way, but it could involve too many calculations and therefore might not be useful in practice. In this example, you would have to calculate the probability of exactly 2 people sharing a birthday, of exactly 3 sharing a birthday, 4 sharing a birthday, and so on, and add them all up – too much work, wouldn’t you agree? Much simpler to just calculate the probability for no shared birthday and subtract from 1.

Last edited by Alg Num Theory (2018-03-09 03:01:56)

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Me, or the ugly man, whatever (3,3,6)

Hannibal lecter

Member

Registered: 2016-02-11

Posts: 392

Re: why I can't calculate the probability of birthday problem without...

I can't imagine how could it involve too many calculation? can you give me  a hint

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Wisdom is a tree which grows in the heart and fruits on the tongue

Alg Num Theory

Member

Registered: 2017-11-24

Posts: 693

Website

Re: why I can't calculate the probability of birthday problem without...

If you can’t imagine, then don’t – just try the calculations and see for yourself!

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Me, or the ugly man, whatever (3,3,6)

Hannibal lecter

Member

Registered: 2016-02-11

Posts: 392

Re: why I can't calculate the probability of birthday problem without...

how to start calculating

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Wisdom is a tree which grows in the heart and fruits on the tongue