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positive-outcome (publication) bias

Positive-outcome (or "publication") bias is the tendency to publish research with a positive outcome more frequently than research with a negative outcome. Negative outcome refers to finding nothing of statistical significance or causal consequence, not to finding that something affects us negatively.

Positive-outcome bias also refers to the tendency of the media to publish medical study stories with positive outcomes much more frequently than such stories with negative outcomes. Media bias may be due to scientific journal bias, but the latter seems to be due mainly to researchers not submitting negative outcome studies for publication (the file-drawer effect), rather than to bias on the part of publication or peer review editors.

further reading

Publication Bias: The “File-Drawer” Problem in Scientific Inference by Jeffrey D. Scargle. Journal of Scientific Exploration, Vol. 14, No. 1, pp. 91–106, 2000.

Publication bias: the problem that won't go away by K. Dickersin and Min YI

The existence of publication bias and risk factors for its occurrence by K. Dickersin

Publication bias: evidence of delayed publication in a cohort study of clinical research projects  by Jerome M Stern and R John Simes

Positive-Outcome Bias and Other Limitations in the Outcome of Research Abstracts Submitted to a Scientific Meeting by Michael L. Callaham, MD; Robert L. Wears, MD; Ellen J. Weber, MD; Christopher Barton, MD; Gary Young, MD

Bias against negative studies in newspaper reports of medical research by G. Koren and N. Klein

Easterbrook PJ, Berlin JA, Gopalan R, Matthews DR. "Publication bias in clinical research," Lancet. 1991;337:867-872.

Moscati R, Jehle D, Ellis D, Fiorello A, Landi M. "Positive-outcome bias: comparison of emergency medicine and general medicine literatures," Acad Emerg Med. 1994;1:267-271.


When scientists, scholarly reviewers, and the media focus only on the most sensational results of research studies, the resulting distortions can harm scientific progress and the public What about all the studies that don’t succeed? Are peer-reviewers less likely to approve publication of a finding saying that a treatment doesn’t work? Might researchers be tempted to sweep uninteresting results under the rug? Unfortunately, in many fields, the answer to these questions appears to be “yes.”


new It's a scandal drug trial results are still being withheld by Dr. Ben Goldacre "...the chances of a completed trial being published are roughly 50%....trials with positive results are twice as likely to be published as those with negative results...." [/new]

The drugs don't work: a modern medical scandal by Dr. Ben Goldacre "Seven trials had been conducted comparing reboxetine against a placebo. Only one, conducted in 254 patients, had a neat, positive result, and that one was published in an academic journal, for doctors and researchers to read. But six more trials were conducted, in almost 10 times as many patients. All of them showed that reboxetine was no better than a dummy sugar pill. None of these trials was published."--Ben Goldacre [The Guardian article is an excerpt from Bad Pharma: How Drug Companies Mislead Doctors and Harm Patients published in the UK September 25, 2012; to be published in the U.S. January 8, 2013.]

Last updated 13-Jan-2014

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