Descriptive statistics and graphical displays.

Statistics is a broad mathematical discipline dealing with techniques for the collection, analysis, interpretation, and presentation of numerical data. Data are information used for reasoning, discussion, or calculation; data are the foundation of modern scientific inference. Data may be obtained by a formal sampling procedure, by recording responses to experimental conditions, or by observing a process repeatedly over time. Once data are collected, statistical analysis typically begins by calculating descriptive statistics—numbers that characterize features of those specific data—and by presenting the descriptive statistics in tables or graphs. In contrast, inferential statistics—statistics for making inferences about the populations from which data are sampled—is a related, broader category of statistical analysis. Forthcoming articles in this series will cover topics in inferential statistics. In this article, we consider elementary descriptive statistics. Similar material can be found in standard statistical textbooks or online.1–4