'The world is full of obvious things which nobody by any chance ever observes.'
Sherlock Holmes (in Sir A. Conan Doyle's The Hound of the Baskervilles)
Chapter 5 is about examining how pairs of continuous variables are related.
Drawing scatterplots is one of the first things statisticians do when looking at datasets. Scatterplots can reveal structure that is not readily apparent from summary statistics or from models, and they are relatively easy to understand and present. They are the basis of the Gapminder displays [Rosling, 2013] used so effectively by Hans Rosling to draw attention to patterns of world development.
The major role of scatterplots ...