Why Most Published Research Findings Are False

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PLoS Med. 2005 Aug;2(8):e124. Epub 2005 Aug 30.

Why most published research findings are false.

Ioannidis JP.

Department of Hygiene and Epidemiology, University of

Ioannina School of Medicine, Ioannina, Greece.

jioannid@...

There is increasing concern that most current

published research findings are false. The probability

that a research claim is true may depend on study

power and bias, the number of other studies on the

same question, and, importantly, the ratio of true to

no relationships among the relationships probed in

each scientific field. In this framework, a research

finding is less likely to be true when the studies

conducted in a field are smaller; when effect sizes

are smaller; when there is a greater number and lesser

preselection of tested relationships; where there is

greater flexibility in designs, definitions, outcomes,

and analytical modes; when there is greater financial

and other interest and prejudice; and when more teams

are involved in a scientific field in chase of

statistical significance. Simulations show that for

most study designs and settings, it is more likely for

a research claim to be false than true. Moreover, for

many current scientific fields, claimed research

findings may often be simply accurate measures of the

prevailing bias. In this essay, I discuss the

implications of these problems for the conduct and

interpretation of research.

PMID: 16060722 [PubMed - in process]

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