Name
Abstract | ||
|---|---|---|
Risk-limiting audits (RLAs) offer a statistical guarantee: if a full manual tally of the paper ballots would show that the reported election outcome is wrong, an RLA has a known minimum chance of leading to a full manual tally. RLAs generally rely on random samples. Stratified sampling-partitioning the population of ballots into disjoint strata and sampling independently from the strata-may simplify logistics or increase efficiency compared to simpler sampling designs, but makes risk calculations harder. We present SUITE, a new method for conducting RLAs using stratified samples. SUITE considers all possible partitions of outcome-changing error across strata. For each partition, it combines P-values from stratum-level tests into a combined P-value; there is no restriction on the tests used in different strata. SUITE maximizes the combined P-value over all partitions of outcome-changing error. The audit can stop if that maximum is less than the risk limit. Voting systems in some Colorado counties (comprising 98.2% of voters) allow auditors to check how the system interpreted each ballot, which allows ballot-level comparison RLAs. Other counties use ballot polling, which is less efficient. Extant approaches to conducting an RLA of a statewide contest would require major changes to Colorado's procedures and software, or would sacrifice the efficiency of ballot-level comparison. SUITE does not. It divides ballots into two strata: those cast in counties that can conduct ballot-level comparisons, and the rest. Stratum-level P-values are found by methods derived here. The resulting audit is substantially more efficient than statewide ballot polling. SUITE is useful in any state with a mix of voting systems or that uses stratified sampling for other reasons. We provide an open-source reference implementation and exemplar calculations in Jupyter notebooks. |
Year | DOI | Venue |
|---|---|---|
2018 | 10.1007/978-3-030-00419-4_12 | Lecture Notes in Computer Science |
Field | DocType | Volume |
Population,Audit,Voting,Suite,Computer science,Polling,Ballot,Sampling (statistics),Stratified sampling,Statistics | Conference | 11143 |
ISSN | Citations | PageRank |
0302-9743 | 1 | 0.43 |
References | Authors | |
4 | 4 | |
Name | Order | Citations | PageRank |
|---|---|---|---|
| Kellie Ottoboni | 1 | 1 | 1.11 |
| Philip B. Stark | 2 | 90 | 16.42 |
| Mark Lindeman | 3 | 18 | 2.69 |
| Neal McBurnett | 4 | 42 | 4.86 |