Even a simple technique such as sorting a set of class marks into order can highlight features that are not evident in a table of the raw data. However, information can be extracted more easily if the marks are displayed graphically.
We start by examining a simpler data structure — a single set of marks from one class in isolation. Data of this form are called a batch of numbers, or a univariate numerical data set.
This chapter describes some simple ways to display the variability in a batch of marks, and gives some examples of the types of information that may be learned from these displays.