From: Kathy Dopp <kathy_dot_dopp_at_gmail_dot_com>

Date: Sat Jul 15 2006 - 21:27:26 CDT

Date: Sat Jul 15 2006 - 21:27:26 CDT

*>
*

*>
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*> Stephanie wrote:
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*> What does "random" mean???
*

*>
*

*> Here's a concern I have and don't know what to do with:
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*>
*

*> How do governing bodies implement "randomness"? We talk of "routine
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*> random audit", but how, in fact, would the precincts be chosen?
*

((OK, here are the details: Philly is divided into 66 "wards", each

*> of which has between 20 and 30 precincts. Each precinct has (at
*

*> least) two voting machines.
*

Stephanie,

In case you have not already discovered this, the Brennan Center report has

some appendices with suggested methods for random selection. The Brennan

Center report also has a mathematical formula that I checked (it seems to be

correct) for deciding how many precincts to audit.

Today, in a few spare minutes, I took the Brennan Center formula for

deciding how many precincts to audit

[using the margin between the two candidates (as someone on this list had

suggested, and I originally disagreed with because I did not, until the

Brennan Center report appendices, see how to make the assumed fraction of

machines/votes compromised dependent on the margin between the candidates in

such a way as to make sure that the desired probability for detecting any

outcome-altering vote miscounts in any race was achieved]

I calculated the number of precincts to audit to obtain a desired

probability for detecting the fraction of machines that would have to be

corrupted to alter the outcome of a particular election, given the margin

between the candidates.

I used the Brennan Center report assumption that, at most, 30% of ballots

would be altered on any one machine, which seems reasonable to me. This

would cause a 60% swing in the margin on that machine.

I haven't found the time yet to doublecheck my calcs. Would you like to

help me double-check them and write a short paper on it?

---- Kathy Dopp http://electionarchive.org National Election Data Archive Dedicated to Accurately Counting Elections Subscribe to announcements by emailing election-subscribe@uscountvotes.org Please donate or volunteer. "Enlighten the people generally, and tyranny and oppressions of body and mind will vanish like evil spirits at the dawn of day," wrote Thomas Jefferson in 1816

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Received on Mon Jul 31 23:17:05 2006

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