ALPHA: Audit that Learns from Previously Hand-Audited Ballots
Philip B. Stark

TL;DR
ALPHA is a versatile, efficient election audit method that generalizes BRAVO, accommodating various sampling techniques, social choice functions, and audit types, often requiring significantly smaller samples especially when vote reports are inaccurate.
Contribution
ALPHA introduces a flexible, generalized election audit framework that overcomes BRAVO's limitations, supporting diverse sampling methods, social choice functions, and audit types with improved efficiency.
Findings
ALPHA works with sampling with and without replacement, including Bernoulli sampling.
ALPHA achieves smaller sample sizes than BRAVO when vote reports are inaccurate.
ALPHA applies to all social choice functions covered by SHANGRLA.
Abstract
BRAVO, the most widely tried method for risk-limiting election audits, cannot accommodate sampling without replacement or stratified sampling, which can improve efficiency and may be required by law. It applies only to ballot-polling audits, which are less efficient than comparison audits. It applies to plurality, majority, super-majority, proportional representation, and ranked-choice voting contests, but not to many social choice functions for which there are RLA methods, such as approval voting, STAR-voting, Borda count, and general scoring rules. And while BRAVO has the smallest expected sample size among sequentially valid ballot-polling-with-replacement methods when reported vote shares are exactly right, it can require arbitrarily large samples when the reported reported winner(s) really won but reported vote shares are wrong. ALPHA is a simple generalization of BRAVO that (i)…
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Taxonomy
TopicsSports Analytics and Performance · Law, Economics, and Judicial Systems · Legal and Constitutional Studies
