Audit

Purpose of Audit• Quality assurance procedure• Check accuracy of machine tally of ballots• Ballots for a contest are sampled, manually verified, and results checked

against vote tabulation

Boulder County’s Audit• Risk-minimizing approach – minimize risk of confirming an incorrect election

outcome• Meets “higher level of statistical confidence” part of CRS 1-7-514• Selecting contests – probability proportional to the inverse of the contests’

margin. Close contests more likely to be selected.• Selecting Ballots – statistical algorithm which uses the contest’s margin,

weighting by the number of times the contest appears in a batch, and random selection.

• Uncontested contests ignored

AuditContest & Batch Selection

MBB 3 Tally…. MBB 2 MBB 1

Batch Reporting

ZeroCum 1Cum 2…Cum n

Contest Selection Batch Selection

Weight contests by relative Margin Create Individual MBB Reports

• M margin• V number of participating voters

Weight batches by # times the contest appears in the batch

Randomly select Randomly select

Contest SelectionExample

Ballots Cast

Abs Margin

Rel Margin (% margin)

1/%margin Weight Cumulative Weight

Contest 1 10000 10 10/10000 = 0.001

1000 1000/1150 = 0.870

0.8700

Contest 2 10000 100 100/10000 = 0.01

100 100/1150 = 0.087

0.9570

Contest 3 10000 200 200/10000 = 0.02

50 50/1150 = 0.043

1.0000

1150 1.0

0 0.8700 0.9570 1.0

Contest 1 C 2 C 3

Contest SelectionCaveats

• Select contests one at a time until the audit budget has been reached.

• Contests having unopposed candidates (or no candidates) will not be audited.

• Contests involved in a recount will be ignored. Their results will be audited after the recount.

Batch Selection

Algorithm Used – Negative Exponential (NEGEXP)

• Proposed in 2008 by Aslam, Popa, and Rivest• Ballot batches selected for audit with probability based on the number of times

the contest appears in the batch.• Number of batches to audit determined by the desired confidence that any

outcome-impacting error, if present, would be found.• Better operational efficiency in large elections.• Requires a large number of random numbers use random number generator

Additional Constraints

• Additional batches added to ensure all scanners are audited at least once.• Canvass board may nominate batches to be audited.

SUN MON TUES WED THUR FRI SAT6/24Election Day

6/25Provisionals

6/26Provisionals

6/27Provisionals2PM Audit Kick-off

6/28

6/299:30 am Audit batch pull

6/309:30 am Audit

7/19:30 am Audit2PM Initial Data Review

7/2Provisionals8-day Ballot processing9:30 am Audit

7/39:30 am Auditif needed3PM Data Q&A and final Election Data Provided

7/44th of July

7/5

7/6 7/72PM Final Canvass Board meeting

7/8 7/9 7/10 7/11 7/12

7/13 7/14 7/15 7/16 7/17 7/18 7/19

2014 Primary Election CanvassReconciliation & Audit Schedule