Bayes Factors: What they are and what they are not

Michael Lavine and Mark J. Schervish


Bayes factors have been offered by Bayesians as alternatives to P-values (or significance probabilities) for testing hypotheses and for quantifying the degree to which observed data support or conflict with a hypothesis. Schervish (1996) showed how the interpretation of P-values as measures of support suffers a certain logical flaw. In this paper, we show how Bayes factors suffer that same flaw. We investigate the source of that problem and consider what are the appropriate interpretations of Bayes factors.

Keywords: Measures of support; P-values

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