B – Reporting P values in the biomedical literature

Chavalarias D, Wallach JD, Li AH, et al. Evolution of reporting P values in the biomedical literature, 1990-2015. JAMA 2016;315(11):1141-1148
(doi: 10.1001/jama.2016.1952)

Many research fields in biomedicine and other disciplines use statistical testing methods that report P values to convey inferences about study results. There is increasing concern that P values are often misused, misunderstood, and miscommunicated, and there is mounting evidence from diverse fields that reporting biases tend to preferentially select the publication and highlighting of results that are statistically significant, as opposed to “negative” results. Such biases could have major implications for the reliability of the published scientific literature. In this analysis of P values reported in MEDLINE abstracts and in PMC articles from 1990-2015, more MEDLINE abstracts and articles reported P values over time, almost all abstracts and articles with P values reported statistically significant results and, in a subgroup analysis, few articles included confidence intervals, Bayes factors, or effect sizes.