An Experimental Study of Jury Decision Rules

Guarnaschelli, Serena; McKelvey, Richard D.; Palfrey, Thomas R.

doi:10.2307/2586020

Cited by 235 publications

(187 citation statements)

References 17 publications

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“…The procedures and framing of the experiment were based on the Condorcet jury "jar" interface introduced by Guarnaschelli et al (2000) and adapted by Battaglini et al (2008Battaglini et al ( , 2010 in their initial laboratory studies of the swing voter's curse. The two states of the world are represented as two jars, a red jar and a blue jar.…”

Section: Experimental Design and Hypothesesmentioning

confidence: 99%

Ignorance and bias in collective decisions

Elbittar

Gomberg

Martinelli

et al. 2020

Journal of Economic Behavior & Organization

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ABSTRACT. We study theoretically and experimentally a committee with common interests. Committee members do not know which of two alternatives is the best, but each member can acquire privately a costly signal before casting a vote under either majority or unanimity rule. In the experiment, as predicted by Bayesian equilibrium, voters are more likely to acquire information under majority rule, and attempt to counter the bias in favor of one alternative under unanimity rule. As opposed to Bayesian equilibrium predictions, however, many committee members vote when uninformed. Moreover, uninformed voting is strongly associated with a lower propensity to acquire information. We show that an equilibrium model of subjective prior beliefs can account for both these phenomena, and provides a good overall fit to the observed patterns of behavior both in terms of rational ignorance and biases. On trouve de plus, que si la probabilité de la voix de chaque Votant est plus grande que 1 2 , c'est-à-dire, s'il est plus probable qu'il jugera conformément à la vérité, plus le nombre des Votans augmentera, plus la probabilité de la vérité de la décision sera grande : la limite de cette probabilité sera la certitude [. . . ] Une assemblée très-nombreuse ne peut pas être composée d'hommes très-éclairés; il est même vraisemblable que ceux qui la forment joindront sur bien des objets beaucoup d'ignorance à beaucoup de préjugés. Condorcet (1785) [1986, p. 29-30]

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Section: Experimental Design and Hypothesesmentioning

confidence: 99%

Ignorance and bias in collective decisions

Elbittar

Gomberg

Martinelli

et al. 2020

Journal of Economic Behavior & Organization

Self Cite

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“…However, they do not explore the possibility of defining special majority voting in terms of a required absolute margin. Feddersen and Pesendorfer (1998), Coughlan (2000), Gerardi (2000), and Guarnaschelli, McKelvey and Palfrey (2000) all discuss the Condorcet jury theorem in relation to unanimous jury verdicts. Kanazawa (1998) provides a Condorcet jury theorem for special majority voting with high individual competence.…”

Section: An Implication For the Definition Of Special Majority Votingmentioning

confidence: 99%

On the Significance of the Absolute Margin

List¹

2004

The British Journal for the Philosophy of Science

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Abstract.Consider the hypothesis H that a defendant is guilty (a patient has condition C), and the evidence E that a majority of h out of n independent jurors (diagnostic tests) have voted for H and a minority of k:=n-h against H. How likely is the majority verdict to be correct? By a formula of Condorcet, the probability that H is true given E depends only on each juror's competence and on the absolute margin between the majority and the minority h-k, but neither on the number n, nor on the proportion h/n. This paper reassesses that result and explores its implications. First, using the classical Condorcet jury model, I derive a more general version of Condorcet's formula, confirming the significance of the absolute margin, but showing that the probability that H is true given E depends also on an additional parameter: the prior probability that H is true. Second, I show that a related result holds when we consider not the degree of belief we attach to H given E, but the degree of support E gives to H. Third, I address the implications for the definition of special majority voting, a procedure used to capture the asymmetry between false positive and false negative decisions. I argue that the standard definition of special majority voting in terms of a required proportion of the jury is epistemically questionable, and that the classical Condorcet jury model leads to an alternative definition in terms of a required absolute margin between the majority and the minority. Finally, I show that the results on the significance of the absolute margin can be resisted if the socalled assumption of symmetrical juror competence is relaxed.

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“…Guarnaschelli, McKelvey and Palfrey (2000) find strong experimental evidence for the effectiveness of small juries to find "the truth" (in their study they call it "the signal"). If pi=0.7, n=6 and there is no group deliberation, then "[u]nder majority rule, the subjects voted the same direction as their signals more than 94% of the time."…”

Section: The Condorcet Jury As a Wise Social Plannermentioning

confidence: 99%

Condorcet’s Jury Theorem as a Rational Justification of Soft Paternalistic Consumer Policies

Dold

2016

Nudging - Possibilities, Limitations and Applications in European Law and Economics

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Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. Terms of use: Documents in AbstractThe objective of this note is to revisit the meaningfulness of the Condorcet Jury Theorem (CJT) and apply it to the recent debate on liberal paternalism and consumer protection. The CJT consists of two parts, (a) stating that a jury of experts is always more competent than a single expert given a certain level of competence, and (b) asserting that for large juries, the collective competence approaches infallibility. This note argues that these insights suggest the application of a Condorcet jury voting procedure to the case of nudging boundedly rational consumers. The note proposes a simple calculus for finding an optimal jury size and advocates consumers' metapreferences as the jury's evaluative dimension for designing soft paternalistic policies. JEL Classification: B41, D03, D63, D71

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An Experimental Study of Jury Decision Rules

Cited by 235 publications

References 17 publications

Ignorance and bias in collective decisions

Ignorance and bias in collective decisions

On the Significance of the Absolute Margin

Condorcet’s Jury Theorem as a Rational Justification of Soft Paternalistic Consumer Policies

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