## Abstract

We consider a probabilistic model of round-robin tournaments, or equivalently, Copeland voting, where candidates are the voters. We assume that the outcomes of each game or pairwise vote are jointly independent. In particular, we do not assume that votes arise from voters' ranked orderings of candidates. We can treat such games as pairwise preferences, without assuming any form of transitivity. We prove the #P-completeness of computing the probability of victory. As a consequence, it is #P-hani to manipulate a round-robin tournament by controlling the outcome of a subset of the games to raise the probability of winning above a particular threshhold. These results hold in the restricted case where all probabilities are zero, one half, or one.

Original language | English |
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Title of host publication | AAMAS 2015 - Proceedings of the 2015 International Conference on Autonomous Agents and Multiagent Systems |

Editors | Rafael H. Bordini, Pinar Yolum, Edith Elkind, Gerhard Weiss |

Pages | 1851-1852 |

Number of pages | 2 |

ISBN (Electronic) | 9781450337717 |

State | Published - 2015 |

Event | 14th International Conference on Autonomous Agents and Multiagent Systems, AAMAS 2015 - Istanbul, Turkey Duration: May 4 2015 → May 8 2015 |

### Publication series

Name | Proceedings of the International Joint Conference on Autonomous Agents and Multiagent Systems, AAMAS |
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Volume | 3 |

ISSN (Print) | 1548-8403 |

ISSN (Electronic) | 1558-2914 |

### Conference

Conference | 14th International Conference on Autonomous Agents and Multiagent Systems, AAMAS 2015 |
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Country/Territory | Turkey |

City | Istanbul |

Period | 5/4/15 → 5/8/15 |

### Bibliographical note

Publisher Copyright:Copyright © 2015, International Foundation for Autonomous Agents and Multiagent Systems (www.ifaamas.org). All rights reserved.

## ASJC Scopus subject areas

- Artificial Intelligence
- Software
- Control and Systems Engineering