Case reports are considered the lowest level of evidence, but they are also the first line of evidence, because they are where new issues and ideas emerge. A good case report will be clear about the importance of the observation being reported.
If multiple case reports show something similar, the next step might be a case-control study to determine if there is a relationship between the relevant variables.
The same can be said about airbags and collapsible steering columns.
They all began with a case study that lead to larger research, and eventual change.
When designing safer products, looking to past failures is an excellent way to ensure similar mistakes are not made.
The same can be said for other safety issues in cars. The process to get seatbelts required in all cars started with a case study!
The use of past studies allows additional information without needing to spend more time and money on additional studies.
Using the PTSD issue again is an excellent example of a collective study.
Whether it is psychology, business or the arts, the type of case study can apply to any field.
Explanatory The explanatory case study focuses on an explanation for a question or a phenomenon.