ClipAudit: A Simple Risk-Limiting Post-Election Audit
This addresses election integrity for auditors and policymakers, offering a method that is simpler and more flexible than existing approaches like Bravo.
The paper tackles the problem of verifying election results by proposing ClipAudit, a simple risk-limiting audit that draws ballots until a statistical condition is met, achieving a risk-limit α without depending on the unofficial margin.
We propose a simple risk-limiting audit for elections, ClipAudit. To determine whether candidate A (the reported winner) actually beat candidate B in a plurality election, ClipAudit draws ballots at random, without replacement, until either all cast ballots have been drawn, or until \[ a - b \ge β\sqrt{a+b} \] where $a$ is the number of ballots in the sample for the reported winner A, and $b$ is the number of ballots in the sample for opponent B, and where $β$ is a constant determined a priori as a function of the number $n$ of ballots cast and the risk-limit $α$. ClipAudit doesn't depend on the unofficial margin (as does Bravo). We show how to extend ClipAudit to contests with multiple winners or losers, or to multiple contests.