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From: norman@batcomputer.TN.CORNELL.EDU (Norman Ramsey)
Newsgroups: net.math
Subject: Probability question
Message-ID: <374@batcomputer.TN.CORNELL.EDU>
Date: Wed, 5-Mar-86 12:18:38 EST
Article-I.D.: batcompu.374
Posted: Wed Mar  5 12:18:38 1986
Date-Received: Sat, 8-Mar-86 22:05:53 EST
Reply-To: norman@batcomputer.UUCP (Norman Ramsey)
Organization: Theory Center, Cornell University, Ithaca NY
Lines: 16

Doubtless everyone remembers the old chestnut about how many people you
have to have in a room before it becomes likely that two of them share 
the same birthday (I believe that it's something like 23 people for
probability 1/2, and that with fifty people it approaches certainty).

Well, the other day I got to wondering, with N people in the room, what
is that probability that two of them share the same eyeglass prescription.
(Note that I don't want to count two people who don't need glasses, since
they can't swap glasses, and that's no fun). To define "the same" I'm
willing to say "within a tenth of a diopter" or some such nonsense.

How about it. I know this isn't net.optometry, but does anyone know where
I can find the appropriate statistics? Or does anybody know the answer?

-- 
Norman Ramsey     norman@tcgould.tn.cornell.edu       Pianist at Large