Say is the average increase in shoe size for upper-class people compared to middle-class people: then the Wald test can be used to test whether is 0 (in which case social class has no association with shoe size) or non-zero (shoe size varies between social classes).
There are many different species of vultures and each has a different type of habitat. Turkey vultures are the most prominent of the New World vultures and can be found in Southern Canada, the Continental United States, Mexico, Central America and South America. These vultures live in small caves, beneath bushes, in hollowed out logs, and sometimes in abandoned structures.
Turkey Vultures have a better sense of smell, so Black Vultures often fly higher to watch them and then follow them to a carcass. Turkey Vultures are found all over the US and into Canada, while Black Vultures are seen only in the Southeast and southern Texas. Still, Black Vultures are found in most of South America and are the most numerous vulture in the Western Hemisphere.