The first foundation of the case study is the subject and relevance.
Whilst it will not answer a question completely, it will give some indications and allow further elaboration and hypothesis creation on a subject.
The case study research design is also useful for testing whether scientific theories and models actually work in the real world.
The other main thing to remember during case studies is their flexibility.
Whilst a pure scientist is trying to prove or disprove a hypothesis, a case study might introduce new and unexpected results during its course, and lead to research taking new directions.
It is important to ensure that you realize that a case study cannot be generalized to fit a whole population or ecosystem.
Finally, one peripheral point is that, when informing others of your results, case studies make more interesting topics than purely statistical surveys, something that has been realized by teachers and magazine editors for many years.Basically, a case study is an in depth study of a particular situation rather than a sweeping statistical survey.It is a method used to narrow down a very broad field of research into one easily researchable topic.The argument between case study and statistical method also appears to be one of scale.Whilst many 'physical' scientists avoid case studies, for psychology, anthropology and ecology they are an essential tool.Constantly refer back to your bullet points so that you do not lose focus.It is always a good idea to assume that a person reading your research may not possess a lot of knowledge of the subject so try to write accordingly.The general public has little interest in pages of statistical calculations but some well placed case studies can have a strong impact.The advantage of the case study research design is that you can focus on specific and interesting cases.It is valid to conduct case studies but they should be tied in with more general statistical processes.For example, a statistical survey might show how much time people spend talking on mobile phones, but it is case studies of a narrow group that will determine why this is so.