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   Author  Topic: Probability problem clarified  (Read 327 times)
jarls
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Probability problem clarified  
« on: Nov 9th, 2009, 5:16pm »		 Quote Quote Modify Modify
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.
« Last Edit: Nov 14th, 2009, 4:14pm by jarls » IP Logged
SMQ
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Re: Probability problem  
« Reply #1 on: Nov 9th, 2009, 5:22pm »		 Quote Quote Modify Modify
Er, 1 in nCk = 1 in n!/[k!(n - k)!], pretty much by definition.
 
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Grimbal
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Re: Probability problem  
« Reply #2 on: Nov 10th, 2009, 3:05am »		 Quote Quote Modify Modify
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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