I remember seeing the same thing a year or so ago on this list. I tried
it for the first time this semester with my "refresher" course in
statistics for a class of incoming graduate students. I tossed a coin a
number of times and reported the result as "heads" each time
irrespective of the actual outcome. At the third call a slight snigger
went round the room, clearly emerging disbelief at the fourth and
outright disbelief at the fifth, corresponding to p values of 0.125,
0.0625, 0.03215 based on a hypothesis of a fair coin and a truthful
instructor. It appears, indeed, that 0.05 reasonably represents the
level at which human scepticism begins to emerge.
David Evans
School of Marine Science
College of William & Mary
Gloucester Point, VA
"John W. Kulig" wrote:
>
> I have been searching for some "psychological" data on the .05 issue - I
> know it's out there but haven't found it yet. It went something like this:
> Claim to a friend that you have a fair coin. But the coin is not fair. Flip the
> coin (you get heads). Flip it again (heads again). Ask the friend if s/he wants
> to risk $100 (even odds) that the coin is not fair. At what point does the
> friend (who is otherwise ignorant of p issues) wager a bet that the coin is not
> fair? I have heard that after 5 or 6 heads the friend is pretty sure it's a bad
> coin - or at least a trick (at this point we cross .05 on the binomial chart)
> .05 may be rooted in our general judgment/perception heuristics -
> understandable in evolutionary terms if we examine the everyday situations we
> make these judgments in. Of course the relative risks of I versus II would
> matter (e.g. falsely accusing and starting a brawl vs. losing to a con artist).
> I will try to locate some research data on this .... or I'll flip a few coins
> in my next statistically naive class.
>
> --
> ---------------------------------------------------------------
> John W. Kulig [EMAIL PROTECTED]
> Department of Psychology http://oz.plymouth.edu/~kulig
> Plymouth State College tel: (603) 535-2468
> Plymouth NH USA 03264 fax: (603) 535-2412
> ---------------------------------------------------------------
> "What a man often sees he does not wonder at, although he knows
> not why it happens; if something occurs which he has not seen before,
> he thinks it is a marvel" - Cicero.
>
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