From: Dan Fabulich (dfabulich@warpmail.net)
Date: Mon Oct 28 2002 - 17:08:15 MST
Eliezer S. Yudkowsky wrote:
> Suppose that we flip a fair coin 20 times, and that a biased sampling
> procedure then randomly selects 5 coinflips from the set of coinflips that
> came up heads and reports on those coinflips; if there aren't 5 coinflips
> that came up heads, the biased sampling procedure reports all available
> heads and enough randomly selected tails to make up the gap.
You don't say how it picks which heads to report. Randomly? Does it pick
the first 5 heads?
> Suppose the biased sampling procedure reports that the first, sixth,
> eleventh, fifteenth, and eighteenth flips came up heads. Is there a
> simple general formula for calculating the probability that any given
> other coinflip came up tails? Clearly the probability is greater than
> 50%, but by how much?
If it picks the *first* 5 heads, then you can be certain that all of the
un-reported flips below 18 must be tails. Is that what you want? (I
presume not, but it's worth clarifying.)
-Dan
-unless you love someone-
-nothing else makes any sense-
e.e. cummings
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