Re: Mandatory vote audit law language: A discussion thread-- choosing precincts at random for audit

From: Kathy Dopp <kathy_dot_dopp_at_gmail_dot_com>
Date: Sat Jul 15 2006 - 21:27:26 CDT

> Stephanie wrote:
> What does "random" mean???
> Here's a concern I have and don't know what to do with:
> How do governing bodies implement "randomness"? We talk of "routine
> 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.


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
National Election Data Archive
Dedicated to Accurately Counting Elections
Subscribe to announcements by emailing
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

OVC-discuss mailing list

= The content of this message, with the exception of any external
= quotations under fair use, are released to the Public Domain
Received on Mon Jul 31 23:17:05 2006

This archive was generated by hypermail 2.1.8 : Mon Jul 31 2006 - 23:17:09 CDT