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Topic: [Fathom] Switching babies
Replies: 2   Last Post: Oct 17, 2004 7:00 PM

 Messages: [ Previous | Next ]
 Pat ballew Posts: 455 Registered: 12/3/04
RE: [Fathom] Switching babies
Posted: Oct 17, 2004 7:05 AM

David,

I think if you put make a collection with four cases in the first
column called x. Just make the formula random() and it will pick four
random values in the zero-one range

and then in column two "baby" use the formula rank(x) and it will assign
each mother a baby.

Then make a variable called "rightbaby" using the formula if
(caseindex=baby){1,0} and it will have a one for each right baby, and a zero
for each wrong baby..

Now collect a measure called "numright" and make the formula sum(rightbaby)
Now resample lots of times and make a graph of how many times each result
appears.

I once wrote a similar thing for the ti-82 (long time ago) to solve the same
problem talking about returning hats... For this interested it is at the
very bottom of http://www.pballew.net/#TI82 look for the ten hats

Hope that works... If you have trouble, send me a note off list and I will
send an attachment.

Pat Ballew
Lakenheath, UK

MathWords http://www.pballew.net/etyindex.html

-----Original Message-----
From: owner-fathom@mathforum.org [mailto://owner-fathom@mathforum.org] On
Behalf Of David Arnold
Sent: Sunday, October 17, 2004 7:33 AM
To: fathom@mathforum.org
Subject: [Fathom] Switching babies

All,

There's a nice example in Workshop statistics. Four mothers have a baby in
the hospital. If the babies are returned to their mothers at random, what
can happen?

The idea involves permuations, where the order of selection is important.
So, 1234 could represent that the first mom got baby 1, the second mom baby
2, the third mom baby 3, and the fourth mom baby 4. Let this represent the
fact that all the moms got the correct baby.

Further, the permutation 1243 would represent the fact that the first two
moms got the correct baby, but the third and fourth moms had their babies
switched.

Can anyone share some ideas on how to simulate this in Fathom?

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Date Subject Author
10/17/04 David Arnold
10/17/04 Pat ballew
10/17/04 Al Sagel