# [EM] IRV vs Plurality (Dave Ketchum)

Kathy Dopp kathy.dopp at gmail.com
Sat Jan 16 14:19:00 PST 2010

```Kristofer,

I don't know about Condorcet auditing because I haven't tried to
figure it out yet, but its mathematics seems to be much simpler than
IRV/STV since only n(n-1) counts are necessary to report for each
audit unit (precinct or whatever.) and I'm sure the fact that
Condorcet counts fit so nicely into an nxn matrix would probably help
the numeric algorithms.

I would need to figure out how what the upper margin error bounds for
all candidate pairs for one Condorcet audit unit (precinct or other
publicly reported) matrix are, given the reported vote counts and
number of ballots cast in each. Once that is done, I think figuring
out several methods would come simply.  It seems very do-able to me,
but it would take me who knows how many days or weeks or even months
of studying the problem to figure out exactly.  As soon as Condorcet
methods are adopted for a public federal, or perhaps even state-level
election, I would definitely not oppose implementation of the
Condorcet method with the minimum margin method of resolving cycles
and would be happy to try to develop the post-election auditing
mathematics for it.

Kathy

On Sat, Jan 16, 2010 at 4:55 PM, Kristofer Munsterhjelm
> Kathy Dopp wrote:
>>
>> On Sat, Jan 16, 2010 at 2:54 PM, Abd ul-Rahman Lomax
>> <abd at lomaxdesign.com> wrote:
>>>
>>> results. Generally, voting security people like to use audits that select
>>> a
>>> sample of votes and look for errors, then they use statistical analysis
>>> to
>>> estimate the overall error in result probability. That's not nearly as
>>> easy
>>> with IRV, because IRV is a chaotic method, sensitive to a single vote
>>> error
>>> that ripples into shifting many votes. With many places where that single
>>> vote error can occur.
>>>
>>> At least that's my understanding, I'd defer to Kathy on this!
>>
>> Yes, IRV is virtually impossible (practically) to audit in a way that
>> the general public could understand. There are several ways to
>> manually audit IRV/STV as far as publicly reporting the tallies and
>> randomly selecting them:
>>
>> 1. report every rank choice ballot for every voter and make a humanly
>> readable mark on every ballot (preferrably after the voter casts or as
>> the voter casts the ballot to avoid vote-buying) that is also listed
>> alongside the ballot choices, and then randomly select ballots, or
>>
>> 2. publicly report all the tallies for each possible unique rank
>> choice vote for each precinct (a huge number larger than the number of
>> voters who vote in most precincts if there are many candidates
>> running), and then randomly sample from those, or
>>
>> 3. manually count 100% of the ballots
>
> Offtopic, perhaps, but would these problems hold for Condorcet as well? Both
> IRV and Condorcet methods are ranked-ballot ones, though I guess auditing
> Condorcet would be easier since it's precinct-summable. It doesn't appear to
> be as easy as Plurality, though, because you can't tie "A beat B N times" to
> what kind of votes the N voters submitted other than that they ranked A
>

--

Kathy Dopp

Town of Colonie, NY 12304
phone 518-952-4030
cell 518-505-0220

http://electionmathematics.org
http://kathydopp.com/serendipity/

Realities Mar Instant Runoff Voting
http://electionmathematics.org/ucvAnalysis/US/RCV-IRV/InstantRunoffVotingFlaws.pdf

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