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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 Condorcet's formula, 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 so-called assumption of symmetrical juror competence is relaxed.

*Introduction*

*The classical Condorcet jury model and the Condorcet jury theorem*

*The significance of the absolute margin for the degree of belief we attach to the hypothesis given the evidence*

*The significance of the absolute margin for the degree of support the evidence gives to the hypothesis*

*An implication for the definition of special majority voting*

5.1 *Making positive decisions if and only if the truth of the hypothesis is beyond any reasonable doubt*

5.2 *Tracking the truth in the limit*

5.3 *Summary*

*The jury model without the assumption of symmetrical competence*

*Concluding remarks*

*Journal Article.*
*0 words.*

*Subjects: *
Philosophy of Science
;
Science and Mathematics

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