in an instrumental case study , a case is considered a suitable example of a more general class of such instances to be useful in exploring a general issue where the nature of the research issue/questions suggests more will be learnt by studying a particular case in detail than by surveying many cases in less depth. So the research may be motivated by a desire to develop understanding of particular kinds of events or processes (i.e., theory-directed), and the case is an instrument for addressing the research questions.