Ames 60 percent, one row per ballot: evidence account

How the sample was chosen

This seed names no sealed machine records and no published box list. This account does not show the sample was chosen before anyone could see the ballots.

The contest

Title: Ames 60 percent, one row per ballot

Candidates: Ames, Baird.

Records in this count: 500.

Ballot file: comparison-cvrs

Source: Synthetic committed CVRs for the Lindeman and Stark 2012 comparison example (diluted margin 20%).

300 ballots mark Ames first, 200 mark Baird first. Each row is one physical ballot. Paper rankings are omitted, so they match the committed CVRs. This is a fixture, not a sealed container.

Where the records sat:

One stack of 500 records. There is no ballot manifest of sealed containers.

No container custody was supplied.

What was configured

Configuration version: comparison-cvrs-plurality-v1.

Configuration fingerprint (SHA-256): 2e17d1a30e4d099b225842a35a8404c27ed52d9fca06faad6392f4cfd0574601.

Counting rule: plurality.

Ballot rules used: Two or more marks at one rank end the ballot there; 2 ranks in a row left blank end the ballot; a candidate marked again lower down counts as a rank left blank.

Ballot file: comparison-cvrs. A third party with this file can rerun the count.

Audit: ballot-level comparison risk-limiting audit. Public seed: plurality-comparison. Risk limit 10% (used in the audit math).

Plain-language configuration (check against statute intent):

Configuration version: comparison-cvrs-plurality-v1

Fingerprint (SHA-256): 2e17d1a30e4d099b225842a35a8404c27ed52d9fca06faad6392f4cfd0574601

Election: Ames 60 percent, one row per ballot

A demonstration configuration over synthetic committed CVRs. No real election was counted under it.

Audit risk limit is the 10% limit this package uses for risk-limiting audits; it is not a claim about any statute.

Contests and candidates:

Ames 60 percent, one row per ballot (comparison-cvrs): Ames; Baird.

Counting rule: plurality (most first choices).

Tiebreak: not used under this counting rule.

Ballot rules (how marks become a ranking):

Two or more marks at one rank: the ballot counts up to that rank and no further.

A candidate marked again lower down: that rank counts as a rank left blank.

2 ranks in a row left blank: the ballot counts up to there and no further.

A mark for anyone not on the ballot: a mark, so the rank is not blank, but never a vote.

Audit risk limit: 10%. A risk-limiting audit that runs under this configuration stops when the sample confirms the outcome at that limit, or sends the contest to a full hand count.

How a ballot is counted and how an audit stops are fixed by this version. Changing any of the lines above requires a new version id.

The count

What follows is the counting account under plurality, including every intermediate step.

What was counted

Ballots in this count: 500.

Ballots from: Synthetic committed CVRs for the Lindeman and Stark 2012 comparison example (diluted margin 20%).

300 ballots mark Ames first, 200 mark Baird first. Each row is one physical ballot. Paper rankings are omitted, so they match the committed CVRs. This is a fixture, not a sealed container.

How the marks on a ballot were read:

Two or more marks at one rank: the ballot counts up to that rank and no further.

A candidate marked again lower down: that rank counts as a rank left blank.

2 ranks in a row left blank: the ballot counts up to there and no further.

A mark for anyone not on the ballot: a mark, so the rank is not blank, but never a vote.

The rankings the ballots form, and how many ballots form each. A candidate a ranking does not name is ranked last on those ballots.

The count

Each ballot counts once, for the candidate it marks first.

Ballots counting for a candidate: 500.

Ballots marking no candidate: 0.

Ballots stopped by two or more marks at their first rank: 0.

Ames is elected with 300 first choices, more than any other candidate.

Records with no mark, by contest and by machine

At the close of polls, the share of records with no mark in each contest, by contest and by machine. Leaving a contest blank is a voter's right; an outlier below is a question about the ballot or the machine, not a verdict.

The audit

This is the ballot-level comparison test in Lindeman and Stark, A Gentle Introduction to Risk-limiting Audits (2012), section III.B. Risk limit 10%. It is the Kaplan-Markov product (Stark 2010, super-simple comparison) for a plurality, winner versus runner-up. A majority is not required.

A risk-limiting audit does not prove the outcome is right. It has a large chance of forcing a full hand count when the outcome is wrong. If the outcome is right, this test cannot change it.

Reported winner: Ames with 300 first choices. Runner-up: Baird with 200.

Ballots N (every CVR, including undervotes and invalids): 500. Diluted margin m = (300 - 200) / 500 = 20.00%. Max overstatement per ballot u = 2. Inflator gamma = 1.03905. U = 2 gamma / m = 10.3905.

Each draw multiplies the P-value bound by (1 - 1/U) / (1 - o / (2 gamma)). Stop and confirm when the bound is at most 0.1. Stop and count every ballot by hand when the remaining ballots cannot confirm, or when the draw cap is hit without confirming.

Public seed: plurality-comparison

A sealed CVR commitment was not required or verified for this account. Do not read this run as proof the CVRs were fixed before the seed.

Ballot 1 is the first CVR. Sampling is with replacement, SHA-256 of "seed,draw,attempt" mapped onto 1 through N.

The hand read of each drawn ballot is simulated from the per-ballot paper ranking on the fixture (the CVR ranking, when paper is omitted). That is a fixture, not a sealed container. A live audit replaces each simulation with a person reading the paper at that place.

Ballot manifest:

No container custody was supplied.

Draws:

Draws examined: 23. Final P-value bound: 0.0975.

The P-value bound is at most 0.1, so the audit stops. The sample is strong evidence that a full hand count would elect Ames. The outcome stays. Outcome status: audit-confirmed. A risk-limiting audit on the record confirmed this reported outcome at the stated risk limit.

What was found

Decision: confirmed.

There were no CVR/paper disagreements in the sample.

Custody: none supplied. No container custody chain was recorded or verified.

Why it stopped

Decision: confirmed.

The P-value bound is at most 0.1, so the audit stops. The sample is strong evidence that a full hand count would elect Ames. The outcome stays. Outcome status: audit-confirmed. A risk-limiting audit on the record confirmed this reported outcome at the stated risk limit.