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        riddles >> general problem-solving / chatting / whatever >> Probability problem clarified
        
(Message started by: jarls on Nov 9th, 2009, 5:16pm)
Title: Probability problem clarified
Post by jarls on Nov 9th, 2009, 5:16pm
There is a group of n people invited to a meeting. What is the probability that a specific group of k people will show up, given that each person randomly choose whether to go or not.
Title: Re: Probability problem
Post by SMQ on Nov 9th, 2009, 5:22pm
Er, 1 in nCk = 1 in n!/[k!(n - k)!], pretty much by definition.

--SMQ
Title: Re: Probability problem
Post by Grimbal on Nov 10th, 2009, 3:05am
It is not clear how elements are chosen among the n elements.

If exactly k elements are chosen, then the probability is as given by SMQ.

If elements are chosen or discarded one by one by tossing a fair coin, then the probability that exactly the specified group is chosen is 1/2n.


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