Riverbend mayor, one machine's readings altered: 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: Riverbend mayor, one machine's readings altered

Candidates: Ames, Bell, Cruz.

Records in this count: 60.

Ballot file: comparison-altered-machine

Source: Synthetic committed CVRs. No real election was counted.

Sixty ballots, twenty to a precinct, one reading machine to a precinct. The papers hold Ames 22, Bell 28, Cruz 10. reader-3 recorded ten of its Bell papers as Ames, so the machine readings report Ames 32, Bell 18, Cruz 10. Each row is one physical ballot; `paper` is present only where the paper differs from the machine reading. This is a fixture, not a sealed container.

Where the records sat:

No container custody was supplied.

What was configured

Configuration version: comparison-altered-machine-plurality-v1.

Configuration fingerprint (SHA-256): ec0d2dd6a76c3c7772f6112af6dd6cd8dc03f7eeab914c01c19c8e31902de810.

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-altered-machine. A third party with this file can rerun the count.

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

Plain-language configuration (check against statute intent):

Configuration version: comparison-altered-machine-plurality-v1

Fingerprint (SHA-256): ec0d2dd6a76c3c7772f6112af6dd6cd8dc03f7eeab914c01c19c8e31902de810

Election: Riverbend mayor, one machine's readings altered

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

The machine readings report Ames. The simulated papers elect Bell. One machine, reader-3, recorded ten of its Bell papers as Ames.

The box list and the papers are a published sample record. No one observed physical custody of any box.

Contests and candidates:

Riverbend mayor, one machine's readings altered (mayor): Ames; Bell; Cruz.

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: 60.

Ballots from: Synthetic committed CVRs. No real election was counted.

Sixty ballots, twenty to a precinct, one reading machine to a precinct. The papers hold Ames 22, Bell 28, Cruz 10. reader-3 recorded ten of its Bell papers as Ames, so the machine readings report Ames 32, Bell 18, Cruz 10. Each row is one physical ballot; `paper` is present only where the paper differs from the machine reading. 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: 60.

Ballots marking no candidate: 0.

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

Ames is elected with 32 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 32 first choices. Runner-up: Bell with 18.

Ballots N (every CVR, including undervotes and invalids): 60. Diluted margin m = (32 - 18) / 60 = 23.33%. Max overstatement per ballot u = 2. Inflator gamma = 1.03905. U = 2 gamma / m = 8.9061.

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: riverbend

Commitment fingerprint (SHA-256): a35e7c5f592e8ed90652412d522f92bcacee0a761c8a033610df17a60ae834ad

Committed at: 2026-09-08T00:00:00.000Z

A sealed collection was loaded and its fingerprint verified, but commitment was not required for this run.

This account does not claim the CVRs were sealed 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: 15. Final P-value bound: 118.6194.

The sample cannot confirm at this risk limit, so the audit stops sampling and every ballot is counted by hand. The full reading follows.

Re-reading precinct-3

The sample could not confirm Ames at the 10% risk limit.

All of the sample's disagreements came from reader-3, whose ballots sat in precinct-3.

The other machines sampled, reader-1 and reader-2, agreed with the paper on every one of their ballots that was drawn, and precincts whose sampled ballots agreed (precinct-1 and precinct-2) are not sent to a full reading.

The record read here is the paper held for each of the 20 ballots in precinct-3, counted together with the machine readings from the other precincts.

Ballots read: 20.

The reading counts them under plurality, the rule this contest was counted under. What follows is that reading, step by step, so a reader holding the published ballots can rework it.

Each paper is read from the record file, as the sampled papers were. That is a fixture, not a sealed container. A live hand count replaces every one of these readings with a person reading the paper.

Re-reading precinct-3: what was counted

Ballots in this count: 60.

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.

Re-reading precinct-3: the count

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

Ballots counting for a candidate: 60.

Ballots marking no candidate: 0.

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

Bell is elected with 28 first choices, more than any other candidate.

The outcome the record supports

The re-reading of precinct-3 elects Bell. That reading is the outcome that stands, in place of the reported winner Ames. Outcome status: full-hand-count. The audit sent the contest to a full hand count of the record; the hand count, not the machine total, is the outcome.

The reported outcome it replaces rested on reader-3, a machine whose readings the papers did not support: the sample drew 3 of its ballots, and one of them disagreed with the paper held for it. Its sampled ballots sat in precinct-3.

What was found

Decision: full-hand-count.

Every draw whose paper disagreed with its machine record (overstatement o not 0):

The machines that read the sampled ballots:

All of these disagreements came from one machine, reader-3: the sample drew 3 of its ballots, and one of them disagreed with the paper held for it. Its sampled ballots sat in precinct-3.

The other machines sampled, reader-1 and reader-2, agreed with the paper on every one of their ballots that was drawn.

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

Why it stopped

Decision: full-hand-count.

The sample could not confirm Ames at the 10% risk limit.

The re-reading of precinct-3 elects Bell. That reading is the outcome that stands, in place of the reported winner Ames. Outcome status: full-hand-count. The audit sent the contest to a full hand count of the record; the hand count, not the machine total, is the outcome.