Too good to be true: Excess significance in experimental neuroscience

pvalueIn a massive metaanalysis of animal studies of six neurological diseases (EAE/MS; Parkinsons; Ischemic stroke; Spinal cord injury; Intracerebral hemorraghe; Alzheimer’s disease) Tsilidis at al. have demonstrated that the published literature in these fields has an excess of statistically significant results that are due to biases in reporting (PLoS Biol. 2013 Jul;11(7):e1001609). By including more than 4000 datasets (from more than 1000 individual studies!) which they synthesized in 160 metaanalyses they impressively substantiate that there are way too many ‘positive’ results in the literature!  Underlying reasons are reporting bias, including study publication bias, selective outcome reporting bias (where null results are omitted) and selective analysis bias (where data are analysed with different methods that favour ‘positive’ results). Study size was low (mean 16 animals), less than 1/3 of the studied randomized, or evaluated outcome in a blinded fashion, and only 39 of 4140 studies performed sample size calculations!

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