Data may have a rich structure, but we first concentrate on the simplest data structure, a single numerical measurement from each 'individual' in a group. We call data of this form a batch of numbers, or a univariate numerical data set.
Examples of the types of 'individuals' from which we often record data are ...
In this chapter, we describe several common ways to display the variability in a batch of numerical data. We show how such data can provide useful information.