On casing a study versus studying a case

Most methods texts encourage students to define some site or event as a case (noun) that they will go out and study (verb). Cases are defined as real members of a general conceptual class: They exist “out there,” in a sense, before we even arrive. Surveying available cases, researchers are encouraged to ask a series of analytic questions (which ones? how many? how likely? how typical?) and then select in a purposive way to answer a specific research question.