Introduction      Case study refers to the collection and presentation of detailed information about a particular participant or small group, which stresses factors contributing to its success or failure. A form of qualitative descriptive research, the case study looks intensely at an individual or small participant pool, drawing conclusions only about that participant or group and only in that specific context.      * Illustrative Case Studies Serves primarily to make the unfamiliar familiar and to give readers a common language about the topic in question. * Exploratory (or pilot) Case Studies Condensed case studies performed before implementing a large scale investigation. * Cumulative Case Studies Serves to aggregate information from several sites collected at different times. * Critical Instance Case Studies This method is useful for answering cause and effect questions.