Browsing by Author "Blom, Michelle"

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    Auditing Ranked Voting Elections with Dirichlet-Tree Models: First Steps
    (2022) Everest, Floyd; Blom, Michelle; B. Stark, Philip; Stuckey, Peter J.; Teague, Vanessa; Vukcevic, Damjan
    Ranked voting systems, such as instant-runo voting (IRV) and single transferable vote (STV), are used in many places around the world. They are more complex than plurality and scoring rules, presenting a challenge for auditing their outcomes: there is no known risk-limiting audit (RLA) method for STV other than a full hand count. We present a new approach to auditing ranked systems that uses a sta- tistical model, a Dirichlet-tree, that can cope with high-dimensional pa- rameters in a computationally e cient manner. We demonstrate this ap- proach with a ballot-polling Bayesian audit for IRV elections. Although the technique is not known to be risk-limiting, we suggest some strategies that might allow it to be calibrated to limit risk.