"Americans Like to Drive a Lot and Eat Cheese" reports results of the American Time Use Survey of 2003, to be found in the U.S. Statistical Abstract 2004-2005.20 Specifically, drivers in a typical household log 21,200 miles in a year, and the average American consumes 31 pounds of cheese in a year. Is this information about two single quantitative variables or about the relationship between two quantitative variables?