Date:         Sun, 27 Jun 1999 18:02:28 -0400
Reply-To:     "P. Adam Kelly" <pkelly@GARNET.ACNS.FSU.EDU>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         "P. Adam Kelly" <pkelly@GARNET.ACNS.FSU.EDU>
Subject:      Combinatorics?
Comments: To: STUDSTAT@ASUVM.INRE.ASU.EDU
Content-Type: multipart/alternative;

Greetings, I have a question that, I hope, has an easy answer (I just can't
remember how it's done!):

I have a pool of 70 test items, only two of which I'm interested in. My
(computerized) test system administers 20 items out of the pool of 70,
selected at random, to a given test-taker. What is the probability that the
test-taker will see at least one of the two items of interest?

Does it have to do with "n choose k," or what?

Thanks for any replies!

____________________________________________________________
P. Adam Kelly
Ph.D. Candidate, Measurement & Statistics
Dept. of Educational Research
Florida State University
Tallahassee, FL 32306-4453
(850) 575-1097
E-mail: pkelly@garnet.acns.fsu.edu


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