Re: observation selection effects

From: Jesse Mazer <>
Date: Sun, 10 Oct 2004 16:47:47 -0400

John M wrote:
>Dear Kory,
>your argument pushed me off balance. I checked your table and found
>it absolutely true. Then it occurred to me that you made the same
>assumption as in my post shortly prior to yours:
>a priviledge of "ME" to switch, barring the others.
>I continued your table to situations when the #2 player is switching and
>then when #3 is doing it - all the way to all 3 of us did switch and found
>that such extension of the case returns the so called 'probability' to the
>uncalculable (especially if there are more than 3 players) like a many -
>many body problem.

Why would it matter if the other players switch? Based on the description of
the game at I thought the "winning flip" was
determined solely by what each player's original flip was, not what their
final bet was. In other words, if two players get heads and the other gets a
tails, then the winning flip is automatically tails, even if the two players
who got heads switch their bet to tails.

Assuming this is true, it's pretty easy to see why it's better to
switch--although it makes sense to say the winning flip is equally likely to
be heads or tails *before* anyone flips, seeing the result of your own
coinflip gives you additional information about what the winning flip is
likely to be. If I get heads, I know the only possible way for the winning
flip to be heads would be if both the other players got tails, whereas the
winning flip will be tails if the other two got heads *or* if one got heads
and the other got tails.

Received on Sun Oct 10 2004 - 16:50:35 PDT

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