Damjan Vukcevic (Melbourne)

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Damjan Vukcevic


A seminar by Damjan Vukcevic from the University of Melbourne

Title: Statistical audits of election results

Abstract: An election result has been announced.  How can we be confident that it is correct? 

Counting the votes in an election is a complex process.  There are many stages where errors may occur.  With increasing adoption of electronic voting systems around the world, there are ever more opportunities for such errors, or even deliberate tampering.  This has led to rising interest, particularly in the USA, for ways to verify, or ‘audit’, reported election results.  This is also relevant in Australia; for example, Australian Senate elections now include electronic scanning of ballot papers. 

Several methods for conducting election audits have been proposed.  A complete recount of all ballot papers is one obvious way, but this is very expensive.  A more efficient approach is to take a random sample of ballot papers and infer the result statistically.  When the margin of victory is large, a rigorous statistical audit can be quick and cheap.  

Broadly speaking, two different frameworks have motivated the design of auditing methods.  Risk-limiting audits, which follow frequentist principles, and Bayesian audits, which as the name suggests are based on Bayesian inference.  Until now, the methods designed under each framework have been thought of as fundamentally different.  

In this talk, I will start with an introduction to the main ideas and approaches to election audits.  I will present the leading methods and show comparisons of their performance under various scenarios.  Most importantly, I will demonstrate a mathematical equivalence of the frequentist and Bayesian approaches.  This largely unifies the two frameworks and makes it clear that the differences are not fundamental but are to do with how these methods are used.  

Most of the talk will be based on simple election systems, which are mostly relevant to non-Australian elections, but at the end I will discuss ideas on how to extend these results to the more complex preferential voting systems that we use in Australia.

Start date:

11am Thursday, 4 Jul 2019

End date:

12pm Thursday, 4 Jul 2019




Damjan Vukcevic

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