<Li> Illustrative case studies . These are primarily descriptive studies . They typically utilize one or two instances of an event to show the existing situation . Illustrative case studies serve primarily to make the unfamiliar familiar and to give readers a common language about the topic in question . </Li> <Li> Exploratory (or pilot) case studies . These are condensed case studies performed before implementing a large scale investigation . Their basic function is to help identify questions and select types of measurement prior to the main investigation . The primary pitfall of this type of study is that initial findings may seem convincing enough to be released prematurely as conclusions . </Li> <Li> Cumulative case studies . These serve to aggregate information from several sites collected at different times . The idea behind these studies is that the collection of past studies will allow for greater generalization without additional cost or time being expended on new, possibly repetitive studies . </Li> <Li> Critical instance case studies . These examine one or more sites either for the purpose of examining a situation of unique interest with little to no interest in generalization, or to call into question a highly generalized or universal assertion . This method is useful for answering cause and effect questions . </Li>

Who said case study method develops our knowledge