Question

The following description of a statistical study is an excerpt from Understandable Statistics Concepts and Methods, 10 Ed., by Brase and Brase. In 1778, Captain James Cook landed in what we now call the Hawaiian Islands. He gave the islanders a present of several goats, and over the years these animals multiplied into wild herds totaling several thousands. They eat almost anything, including the famous silver sword plant, which was once unique to Hawaii. At one time, the silver sword grew abundantly on the island of Maui ... but each year there seemed to be fewer and ſewer plants. Biologists suspected that the goats were partially responsible for the decline in the number of plants and conducted a statistical study that verified their theory.

Answer 1

The confounding variables could be a lot things here like the weather, temperature, soil, rainfall which might have caused a correlation between increasing herds and depleting silver sword plant. Here, environment(including all the factors above) is the confounding variable between goats and plant. The biologists might have kept goats and plant in different environment and observed how it helped goats thrive and eventually adapting to eat plants in turn depleting the plant's volume.