# [EM] IRV vs Plurality (Dave Ketchum)

Kathy Dopp kathy.dopp at gmail.com
Sat Jan 16 12:30:02 PST 2010

```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

No one, to my knowledge, has tried to develop the mathematics for
sampling sufficiently to verify the accuracy of the election outcomes
to a desired high probability for IRV/STV and I wouldn't want to try.
It has got to be virtually impossible to figure out given how
difficult it has been just to develop the mathematics for the simple
plurality case.  Any method needs to be precinct-summable and possible
for the public to tally the results from whatever tallies are publicly
reported and IRV/STV does not meet that fundamental requirement for
the vast majority of the public who could not even comprehend how many
unique ballot combinations there are, let alone figure out how to
check the tallies from the publicly posted results.

Any other method than IRV/STV (any method that treats all voters'
votes equally) would be easier to figure out how to audit IMO,
although I've not tried to figure out how to audit any other methods
yet as far as the mathematics of sample sizes.

Abd ul your posts are always so informative.  Thank you.

--

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

Voters Have Reason to Worry