Lecture Ten introduces the idea that different variables may move together-sometimes due to causation and at other times due to an unknown influence.
An example involves the perfect (+1.0) correlation between annual number of rum barrels imported into the New England region of the U.S. between the years 1790 and 1820 and the number of churches built each of those years (citation lost).
Discuss this correlation: What does it tell us? Does rum drinking cause church building? Does church building cause rum drinking? Or what else could it tell us? If this correlation shows a cause and effect relationship, what drives what?
If not, why does it exist? What could this correlation be used for?