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Publication bias, also called the positive outcome bias or the "file-drawer problem", arises from the tendency for researchers to publish experimental results that have a positive result (found something), while not publishing findings where the results are negative (found that something did not happen) or inconclusive.
- "Publication bias refers to the tendency of researchers to seek publication of and for journals that accept mainly those studies that find a statistically significant effect, while not publishing studies that don't find an effect." 
The effect of this is that published studies may not be truly representative of all valid studies undertaken, and this bias may distort meta-analyses and systematic reviews of large numbers of studies - on which evidence-based medicine, for example, increasingly relies. The problem may be particularly significant when the research is sponsored by entities that may have a financial interest in achieving favourable results.
Those undertaking meta-analyses and systematic reviews need to take account of publication bias in the methods they use for identifying the studies to include in the review. Among other techniques to minimise the effects of publication bias, they may need to perform a thorough search for unpublished studies, and to use such analytical tools as a funnel plot to quantify the effects of bias.
In September 2004, editors of several prominent medical journals (including the New England Journal of Medicine, The Lancet, Annals of Internal Medicine, and JAMA) announced that they would no longer publish results of drug research sponsored by pharmaceutical companies unless that research was registered in a public database from the start . In this way, negative results should no longer be able to disappear.
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