Re: A paradox? Why not?

[John Denker <jsd@MONMOUTH.COM>]

At 06:12 PM 7/16/99 -0700, James McLean wrote:
> At the risk of displaying my stupidity...
> How does this paradox map onto something which is related to past vs.
> future probability (presumably using the same probability measure)?

Not a stupid question.

When I wrote that sentence, I had in mind the case that you parenthetically
ruled out, namely this:  People have a shocking tendency to calculate the
conditional probability of X given A, and then use it to predict future
values of X in circumstances when they should be using the probability of X
given B.  Similar remarks apply to using the *un*conditional probability
when they should be using one of the conditional probabilities.

If you are careful with your notation, you will find that it becomes easier
to keep track of which probability you are talking about, and harder to
fall into such traps.  The other side of that coin is that you have to be
careful, because our mathematical notation for probabilities is far from
perfect, and our non-mathematical every-day English terminology for
describing probabilities is even worse.

Does that answer your question?