Case study and Written report

Case study noun - A careful study of some social unit (as a corporation or division within a corporation) that attempts to determine what factors led to its success or failure.

Written report and case study are semantically related. In some cases you can use "Written report" instead a noun phrase "Case study".

Written report noun - A written document describing the findings of some individual or group.

Case study and written report are semantically related. Sometimes you can replace phrase "Case study" with "Written report", this phrases are similar.