randomly independent events have the p value being the multiplication of
each event's p value ... so ... p for getting a head in a good coin .... is
.5 ... 2 in a row = .25 ... etc.
here is a table up to 10 in a row of the same side
Row numheads pvalue
1 1 0.500000
2 2 0.250000
3 3 0.125000
4 4 0.062500
5 5 0.031250
6 6 0.015625
7 7 0.007813
8 8 0.003906
9 9 0.001953
10 10 0.000977
i have argued before ... that a value of .05 makes SOME sense IF we
consider the observed data to be "derived" from some model ... like a
sequence of randomly occurring independent events
if one were to flip a coin and then SHOW the result ... AND then ask Ss to
give their perceptions about whether what they see could have occurred by
chance ALONE ... what you will find is that IF you present 4 or 5 or 6 in a
row all being the same ... these are the areas (increasingly so) where
there becomes more and more SUSpicion ... that you would see this IF THE
COIN IS GOOD ... OR THE COIN FLIPPER IS NOT CHEATING ...
thus, the nervousness starts to set in around the .05 .01 areas ... ie, the
times where the probability of that happening ACCORDING TO THE MODEL ...
(coin is good) ... STARTS GETTING RATHER REMOTE
At 12:01 PM 10/20/00 -0400, you 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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