Reveal, Don't Conceal: Transforming Data Visualization to Improve Transparency.

Reports highlighting the problems with the standard practice of using bar graphs to show continuous data have prompted many journals to adopt new visualization policies. These policies encourage authors to avoid bar graphs and use graphics that show the data distribution; however, they provide little guidance on how to effectively display data. We conducted a systematic review of studies published in top peripheral vascular disease journals to determine what types of figures are used, and to assess the prevalence of suboptimal data visualization practices. Among papers with data figures, 47.7% of papers used bar graphs to present continuous data. This primer provides a detailed overview of strategies for addressing this issue by (1) outlining strategies for selecting the correct type of figure depending on the study design, sample size, and the type of variable; (2) examining techniques for making effective dot plots, box plots, and violin plots; and (3) illustrating how to avoid sending mixed messages by aligning the figure structure with the study design and statistical analysis. We also present solutions to other common problems identified in the systematic review. Resources include a list of free tools and templates that authors can use to create more informative figures and an online simulator that illustrates why summary statistics are meaningful only when there are enough data to summarize. Last, we consider steps that investigators can take to improve figures in the scientific literature.

Reinventing Biostatistics Education for Basic Scientists.

Numerous studies demonstrating that statistical errors are common in basic science publications have led to calls to improve statistical training for basic scientists. In this article, we sought to evaluate statistical requirements for PhD training and to identify opportunities for improving biostatistics education in the basic sciences. We provide recommendations for improving statistics training for basic biomedical scientists, including: 1. Encouraging departments to require statistics training, 2. Tailoring coursework to the students' fields of research, and 3. Developing tools and strategies to promote education and dissemination of statistical knowledge. We also provide a list of statistical considerations that should be addressed in statistics education for basic scientists.

Impaired Flow-Mediated Dilation Before, During, and After Preeclampsia: A Systematic Review and Meta-Analysis.

Endothelial dysfunction is believed to play a critical role in preeclampsia; however, it is unclear whether this dysfunction precedes the pregnancy or is caused by pathophysiological events in early pregnancy. It is also unclear for how long vascular dysfunction may persist postpartum and whether it represents a mechanism linking preeclampsia with future cardiovascular disease. Our objective was to determine whether women with preeclampsia had worse vascular function compared with women who did not have preeclampsia by performing a systematic review and meta-analysis of studies that examined endothelial dysfunction using flow-mediated dilation. We included studies published before May 29, 2015, that examined flow-mediated dilation before, during, or after preeclampsia. Differences in flow-mediated dilation between study groups were evaluated by standardized mean differences. Out of 610 abstracts identified through PubMED, EMBASE, and Web of Science, 37 studies were eligible for the meta-analysis. When compared with women who did not have preeclampsia, women who had preeclampsia had lower flow-mediated dilation before the development of preeclampsia (≈20-29 weeks gestation), at the time of preeclampsia, and for 3 years postpartum, with the estimated magnitude of the effect ranging between 0.5 and 3 standard deviations. Similar effects were observed when the analysis was limited to studies that excluded women with chronic hypertension, smokers, or both. Vascular dysfunction predates preeclampsia and may contribute to its pathogenesis. Future studies should address whether vascular changes that persist after preeclamptic pregnancies may represent a mechanistic link with increased risk for future cardiovascular disease.