Appropriate Statistical Design

Audits should produce and scientifically assess evidence about tabulation accuracy while making efficient use of available resources. A risk-limiting audit (RLA) with a small risk limit assures a large chance that an incorrect outcome will be detected and corrected.

Best Practices

  1. Audit design considers current procedures and equipment (e.g. post-election deadlines and whether the voting system supports particular methods of auditing), the variety of contests to be audited, and priorities for how rigorously to audit the various contests. Matching anticipated workload with available time and resources can involve subtle choices and long-term planning.
  2. Statistical experts knowledgeable about post-election audits participate alongside stakeholders in designing the audit process.
  3. Audit units are selected using appropriate publicly verifiable random sampling methods.
  4. Risk-limiting audits are implemented as widely as is considered feasible given the current equipment.
  5. RLAs of contests that span multiple jurisdictions, such as governor or mayor of a city that crosses county lines, are coordinated across jurisdictions or at the state level.
  6. If audits that are not risk-limiting are combined with, or used instead of, RLAs, they use valid risk-measuring designs, in order to assess the strength of the audit evidence that the reported outcomes are correct.
  7. In comparison audits, audit units are defined to be as small as the voting equipment supports: single ballots (or cards) are most efficient; smaller batches are  preferable to larger batches; individual voting machines are preferable to entire precincts; and individual early voting machines daily totals are preferable to entire early voting sites.
  8. If auditing begins before all the ballots have been tabulated (which may be reasonable, e.g., when absentee or provisional ballots are processed late in the canvass), care is taken to incorporate the later-tabulated ballots completely and correctly into the audit process.
  9. Criteria are specified for the circumstances under which additional audit units should be audited, and how many — or, if applicable, under what circumstances a full hand count should be conducted.

(Adapted from Principles and Best Practices for Post-Election Tabulation Audits, 2018)