initials problem

Nov 2009
80
6
What is the probability that in a group of 200 people, at least 2 of them have the same initials?

I'm finding the probability to be about .679. Is this correct?
 

matheagle

MHF Hall of Honor
Feb 2009
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What is the probability that in a group of 200 people, at least 2 of them have the same initials?

I'm finding the probability to be about .679. Is this correct?

Attack this like the birthday problem.
Look at the complement, that there are no matches at all.
 

awkward

MHF Hall of Honor
Mar 2008
934
409
Just a caveat about real-world probabilities. (It's not clear whether this is a textbook exercise or a real-world problem.)

In the "real world", initials are anything but uniformly distributed; there are far more S's then Z's, for example. If you want a real-world answer, you will need to find some data on the distribution of initials and take that into account.
 
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