| Publication Bias |
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DEFINITION :"Publication bias occurs when the publication of research results depends on their nature and direction." {Link without Title} Positive results bias, a type of publication bias, occurs when authors are more likely to submit, or editors accept, positive than null (negative or inconclusive) results. A related term, "the file drawer problem", refers to the tendency for those negative or inconclusive results to remain hidden and unpublished.[http://content.apa.org/journals/bul/86/3/638 Even a small number of studies lost in the file-drawer can result in a significant bias Jeffrey D. Scargle , Journal of Scientific Exploration, 14 (2) 94-106, 2000 . Outcome reporting bias occurs when several outcomes within a trial are measured but these are reported selectively depending on the strength and direction of those results. {Link without Title} A related term that has been coined is HARKing (Hypothesizing After the Results are Known). {Link without Title} For exemple, Skeptics often argues that there is (or at least was) a strong publication bias in the field of parapsychology, leading to a File Drawer Problem . EXAMPLE Suppose that several studies about the influence of power lines on cancer are performed. They are admitted for publication only if they show a correlation with a 95% confidence level. If only the positive results make it to publication, because negative results are just shelved, we do not know how many studies were performed, so it is possible that all the published results are type I errors. EFFECT ON META-ANALYSIS 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 Review s 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 Among other techniques to minimise the effects of publication bias, they may need to perform a thorough search for unpublished studies, and to use such analytical tools as a Funnel Plot to quantify the effects of bias. POSSIBLE EXAMPLE One study'', 2(12):e409, 2005 December.. One possible interpretation of this result is selective publication (publication bias). Ioannidis has inventoried factors that should alert readers to risks of publication bias 1. STUDY REGISTRATION 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 {Link without Title} . In this way, negative results should no longer be able to disappear. SEE ALSO
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