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Are you a shoplifter?


Best Answer Nins_Leprechaun, 06 July 2013 - 10:59 PM

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7 replies to this topic

#1 BMAD

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Posted 06 July 2013 - 09:36 PM

You are conducting a survey where the question is somewhat embarrassing: have you shoplifted within the past 12 months?  You realize that it might be difficult to get honest answers, so you ask your friend the psychology student for advice.  He tells you the following trick:  Ask each person to flip a coin and tell them that if the coin land heads, they should answer the question with a lie, if the coin lands on tails, they should answer 'yes'.  As the person agrees to this before the outcome of the flip is revealed, people would be more likely to participate in such questions.

 

 

Should you follow your friend's advice?  Can you get any meaningful statistic by applying this method?


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#2 Nins_Leprechaun

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Posted 06 July 2013 - 10:59 PM   Best Answer

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#3 vinay.singh84

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Posted 08 July 2013 - 04:18 PM

Spoiler for Hold on

Edited by vinay.singh84, 08 July 2013 - 04:20 PM.

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#4 BMAD

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Posted 08 July 2013 - 04:55 PM

Spoiler for Hold on

To answer your first question, yes. The op was intended to be written this way.

Does the researcher knowing or not knowing the result of the flip matter?
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#5 bonanova

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Posted 10 July 2013 - 10:47 AM

I think Nins_Leprechaun has it. Nice puzzle.


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The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
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#6 gavinksong

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Posted 14 July 2013 - 04:20 PM

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You have a point. The trick in the OP wouldn't really work since saying "no" is pretty much a confession.


Edited by gavinksong, 14 July 2013 - 04:24 PM.

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#7 BMAD

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Posted 14 July 2013 - 04:24 PM

 

Spoiler for Hold on

You have a point. The trick in the OP wouldn't really work since saying "no" is pretty much a confession. But changing the coin setup in the way you described wouldn't work either. The only honest way to make it work would be to tell the surveyee to lie or tell the truth based on how the coin lands, but that wouldn't give you any useful data.

 

I disagree.  This is actually a classic setup that many psychologist use.  Since the participant has the security of the coin flip (if it is secretive toss) the psychologist can calculate using some simple statistics the rate at which one shoplifts (in this case)


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#8 gavinksong

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Posted 15 July 2013 - 12:10 AM

 

 

Spoiler for Hold on

You have a point. The trick in the OP wouldn't really work since saying "no" is pretty much a confession. But changing the coin setup in the way you described wouldn't work either. The only honest way to make it work would be to tell the surveyee to lie or tell the truth based on how the coin lands, but that wouldn't give you any useful data.

 

I disagree.  This is actually a classic setup that many psychologist use.  Since the participant has the security of the coin flip (if it is secretive toss) the psychologist can calculate using some simple statistics the rate at which one shoplifts (in this case)

 

If you follow the current setup, saying "no" is a full confession that you are a shoplifter and saying "yes" means that you may be or may not be. If you change the setup in the way vinay described, saying "yes" means that you are not a shoplifter and saying "no" means that you may or may not be (thus you never have to fully confess that you are a shoplifter).


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