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.
It is best if you make yourself a short list of 4 or 5 bullet points that you are going to try and address during the study.
If you make sure that all research refers back to these then you will not be far wrong.
Scientists are sometimes guilty of becoming bogged down in the general picture and it is sometimes important to understand specific cases and ensure a more holistic approach to research. M.: An example of a study using the case study research design.
Research Proposal Case Study
Some argue that because a case study is such a narrow field that its results cannot be extrapolated to fit an entire question and that they show only one narrow example.
With a case study, even more than a questionnaire or survey, it is important to be passive in your research.
You are much more of an observer than an experimenter and you must remember that, even in a multi-subject case, each case must be treated individually and then cross case conclusions can be drawn.
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.