Case studies: a guide for researchers, educators, and implementers.

Case study is a widely used but poorly understood research method, conducted differently in different disciplines. This paper explores philosophical, theoretical and methodological issues in case study research and outlines how to conduct one. It offers preliminary guidance for policy makers on how to select and use case studies for learning and decision making. In social science research, a case study is a detailed, contextualised account of a clearly delineated, real world phenomenon, prepared prospectively using mostly qualitative methods. Social science case studies can be of various kinds (eg, theoretical or naturalistic, single or multiple, typical or extreme). A public health case study is a historical account of a health threat and how it was managed. An implementation science case study evaluates the implementation of an intervention (usually retrospectively), combining quantitative assessment against predefined objectives with a narrative of how the project unfolded. Educational case studies present real world topics as stories illustrated by data and prompt students to discuss these from different angles. Impact case studies summarise the societal impact of a research programme. Many accounts described as case studies are overly brief and superficial. The paper concludes with a call to improve the quality and consistency (and hence the usefulness) of case studies.