Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 2 (8), e124

Why Most Published Research Findings Are False

Affiliations

Why Most Published Research Findings Are False

John P A Ioannidis. PLoS Med.

Abstract

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.

Conflict of interest statement

Competing Interests: The author has declared that no competing interests exist.

Figures

Figure 1
Figure 1. PPV (Probability That a Research Finding Is True) as a Function of the Pre-Study Odds for Various Levels of Bias, u
Panels correspond to power of 0.20, 0.50, and 0.80.
Figure 2
Figure 2. PPV (Probability That a Research Finding Is True) as a Function of the Pre-Study Odds for Various Numbers of Conducted Studies, n
Panels correspond to power of 0.20, 0.50, and 0.80.

Comment in

Similar articles

See all similar articles

Cited by 1,318 PubMed Central articles

See all "Cited by" articles

References

    1. Ioannidis JP, Haidich AB, Lau J. Any casualties in the clash of randomised and observational evidence? BMJ. 2001;322:879–880. - PMC - PubMed
    1. Lawlor DA, Davey Smith G, Kundu D, Bruckdorfer KR, Ebrahim S. Those confounded vitamins: What can we learn from the differences between observational versus randomised trial evidence? Lancet. 2004;363:1724–1727. - PubMed
    1. Vandenbroucke JP. When are observational studies as credible as randomised trials? Lancet. 2004;363:1728–1731. - PubMed
    1. Michiels S, Koscielny S, Hill C. Prediction of cancer outcome with microarrays: A multiple random validation strategy. Lancet. 2005;365:488–492. - PubMed
    1. Ioannidis JPA, Ntzani EE, Trikalinos TA, Contopoulos-Ioannidis DG. Replication validity of genetic association studies. Nat Genet. 2001;29:306–309. - PubMed

LinkOut - more resources

Feedback