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- %OP%VS4.13 (28-Apr-92), Gerald L Fitton, R4000 5966 9904 9938
- %OP%DP0
- %OP%IRY
- %OP%PL0
- %OP%HM0
- %OP%FM0
- %OP%BM0
- %OP%LM4
- %OP%PT1
- %OP%PDPipeLine
- %OP%WC1026,2262,188,1748,0,0,0,0
- %CO:A,72,72%
- %C%Open The Box
- %C%by Gerald L Fitton
- Keywords:
- Gamble Fitton
-
- The Problem
- This is the statement of the problem copied from an earlier article.
- The solution follows.
-
- I have seen many variants of the following problem. One appeared on
- the February 1993 PipeLine disc under the heading of 'conditional
- probability' but, as it was stated on that disc, it seems to have been
- too difficult for many of you. I've had only incorrect replies. I owe
- the earlier version to Robert Macmillan of Colton Software; this
- version is courtesy of a lady called Marilyn vos Savant quoted in the
- Sunday telegraph on the 7th February 1993. Her version has two
- advantages over the Robert Macmillan version; the first is that it is
- easily testable — the second is that it contains better clues to its
- solution. This is a spreadsheet problem. No prizes for the correct
- answer but you might become famous. How? I'll mention your name!
-
- You are a game show contestant and, through sheer brilliance, you have
- won the right to open one of three boxes. One of the three contains
- the Star Prize, the other two contain Booby Prizes. The game show host
- knows which box contains the Star Prize but, of course, you don't.
-
- You choose a box and tell the game show host and the world wide
- audience of your choice. In accordance with the rules of the box
- opening procedure, the host host opens one of the other two boxes which
- he knows to contain a Booby Prize! At this stage, the rules allow you
- to stick with your original choice or change to the other unopened box.
-
- The question you have to answer is "Would changing to the other
- unopened box improve your chances of winning?"
-
- Now, I don't want to hear of your inspired guesses. I don't want a
- whole load of conditional probability theory, and I don't want to hear
- about Bayes' theorem (or anyone else's for that matter - unless you
- want to name one after me!). What you have to do to achieve fame, if
- not fortune, is to construct a spreadsheet which simulates many runs of
- the 'Open the Box' procedure and use the result to 'prove' your answer
- to the question.
-
- Oh yes! A hint. My son once told me that I'm not a 'Computer person'.
- His definition of a 'Computer person' is someone who starts counting
- (and labelling boxes) with zero instead of one! Label your boxes 0, 1
- and 2. Use the statistical function rand() to decide which box
- contains the Star Prize, which box you have chosen and which box is
- selected by the game show host. If you use one row of the spreadsheet
- per 'trial' then you can total about 100 rows to determine the better
- strategy.
-
- To swop or not to swop? That is the question.
-
-
- The Solution
-
- I have received a good spreadsheet solution from Bruce D Brown which
- you will find in the directory called Brown.
-
- I did receive another solution. It was a well reasoned argument from
- Jonathan Ormond. However, he didn't do it with a spreadsheet so, with
- some reluctance, I have nothing much to say about his solution except
- that it used the usual 'conditional probability' method without the
- usual formula. It was a very good piece of reasoning without any
- mathematical jargon.
-