Exploratory data analysis: numerical summaries

Abstract

The classical way to describe important features of a dataset is to give several numerical summaries. We discuss numerical summaries for the center of a dataset and for the amount of variability among the elements of a dataset, and then we introduce the notion of quantiles for a dataset. To distinguish these quantities from corresponding notions for probability distributions of random variables, we will often add the word sample or empirical ; for instance, we will speak of the sample mean and empirical quantiles. We end this chapter with the boxplot, which combines some of the numerical summaries in a graphical display.