A scatterplot shows the scores on one variable plotted against scores
on a second variable. Below is a plot showing the relationship between
grip strength and arm strength for 147 people working at physically-demanding
jobs. The data are from a case
study in the Rice Virtual Lab in Statistics. The plot shows a very
strong but certainly not a perfect relationship between these two variables.
Scatterplots should almost always be constructed when the relationship
between two variables is of interest. Statistical summaries are no substitute
for a full plot of the data.