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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]