Description
Biologists were interested in whether beetles prefer areas where beavers have cut down cottonwood trees.
(The tree-stumps produce tender green shoots that beetles are thought to like.) 23 circular plots, all of equal area,
were studied. For each plot the researchers counted the number of cottonwood stumps, and also the number of
clusters of beetle larvae found in the plot.source
Basic Practice of Statistics, by Moore and McCabe.