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*From*: John Denker <jsd@AV8N.COM>*Date*: Tue, 3 Aug 2004 16:29:31 -0400

Not exactly physics, but:

1) The forecast for the pre-dawn hours of Thursday, August 12th

is looking good: dark, with probably heavy meteor showers.

http://science.nasa.gov/headlines/y2004/25jun_perseids2004.htm

Folks in Europe might see up to 200 per hour, due to a "new"

filament.

2) Here's an interesting application of statistics. Students

sometimes have a hard time thinking of a probability distribution

as a real, first-class object that you can do computations with.

They think outcomes are real and probabilities are somehow less

than real. So let's do an example: electoral-college votes are

relatively concrete things, while a distribution over votes is

somewhat more abstract, but there is a big advantage if you

have enough sophistication to think in terms of distributions,

so that you can add distributions rather than just adding

votes.

Specifically: On August 1st heard a TV pundit say ``If

the election were held today Kerry would probably get 289

electoral votes and Bush would probably get 232 electoral

votes'' ... which struck me as an astoundingly silly

statement. He was quick to point out that the numbers

are hypothetical, because the election was not being

held that day, but that's not the main problem. The main

problem is twofold:

* First of all, the probability that anybody will get

exactly 289 votes is very small, about two percent.

* More importantly, the winner is not required to

get exactly 289 electoral votes or any other exact number.

The requirement is to get 270 or more.

To look at the issue another way: we need to know how

solid are the tallies predicted by the polls. It is

sufficient to have a one-vote lead if it is absolutely

solid, but far from sufficient to have a large lead in

the polls if the polls have an even larger uncertainty.

This is easy to understand if we think in terms of

probabilities, rather than thinking in terms of votes.

To make a long story short, the probable outcomes (based

on polling data, as of August 3rd) are as follows:

. Kerry Win Bush Win Tie

. 93% 6% 1%

To judge the size of the ``convention bounce'', compare

this with the numbers from a few days earlier: Kerry 84%,

Bush 15%, tie 1%.

For a discussion of the technique, including a link to

a spreadsheet that implements the statistical calculation,

see

http://www.av8n.com/politics/ec-prob.htm

I hope we can have a discussion of the statistical

principles without getting into a partisan wrangle about

the applications and implications for a particular race.

Don't shoot the messenger. I didn't select or fiddle the

data.

Note that the candidates already know this stuff. These

guys are consummate poker-players. The know the odds,

even if they don't necessarily feel like explaining the

odds to other players and/or bystanders.

Now if we could just impart to certain common-taters a

modicum of intelligence and a modicum of respect for

the audience's intelligence....

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