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.
The Old World vultures are close relatives of the hawks and eagles. They have strong talons and beaks and they have a poor sense of smell. The New World vultures are not close relatives of the hawks, but may well be distant relatives of the storks since they share the habit of urinating on their legs to stay cool.