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Open Access Highly Accessed Debate

The probability of cost-effectiveness

Anthony O'Hagan1* and John W Stevens2

Author Affiliations

1 Centre for Bayesian Statistics in Health Economics, University of Sheffield, Sheffield, UK

2 Clinical Sciences, AstraZeneca R&D Charnwood, Loughborough, UK

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BMC Medical Research Methodology 2002, 2:5  doi:10.1186/1471-2288-2-5

Published: 11 March 2002



The study of cost-effectiveness comparisons between competing medical interventions has led to a variety of proposals for quantifying cost-effectiveness. The differences between the various approaches can be subtle, and one purpose of this article is to clarify some important distinctions.


We discuss alternative measures in the framework of individual, patient-level, incremental net benefits. In particular we examine the probability of cost-effectiveness for an individual, proposed by Willan.


We argue that this is a useful addition to the range of cost-effectiveness measures, but will be of secondary interest to most decision makers. We also demonstrate that Willan's proposed estimate of this probability is logically flawed.