Explainer · Plain-language

What is a case study?

A case study is an in-depth, in-context investigation of a single bounded case — a person, group, organisation or event — using multiple sources of evidence to understand it fully.

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Case study research method

A case study concentrates on one bounded case, or a small number, examined intensively rather than extensively. Its defining feature is the use of multiple data sources — interviews, documents, archival records, direct observation and artefacts — triangulated to produce a holistic account. Because the case is studied in its natural context rather than a controlled setting, the method is well suited to complex, real-world phenomena. It can be qualitative, quantitative or mixed, though qualitative case studies are the most common in social research.

Types and designs

Case studies vary by purpose and structure. Exploratory case studies probe a phenomenon when little is known; descriptive ones portray it in detail; explanatory ones examine how and why something happened. A design may be single-case, suited to a unique, critical or revelatory instance, or multiple-case, comparing several cases to strengthen findings. Methodologists such as Robert Yin emphasise rigorous, structured protocols and triangulation, while Robert Stake stresses interpretive, holistic understanding — two influential approaches a researcher can draw on.

Strengths and limits

The strength of a case study is depth: it captures context, nuance and complexity that broad surveys miss, and it can generate hypotheses and theory. Its main limit is generalisability — findings from one case may not transfer to others, and critics raise concerns about researcher bias. Well-designed case studies address this through clear case boundaries, multiple evidence sources, triangulation and transparent reasoning, claiming analytic or theoretical generalisation to concepts rather than statistical generalisation to populations.

Key facts

At a glance

Definition: in-depth study of a single bounded case in real context
Unit: a person, group, organisation, event or programme
Evidence: multiple sources, triangulated (interviews, documents, observation)
Best for: "how" and "why" questions on contemporary phenomena
Designs: single vs multiple case; exploratory, descriptive, explanatory
Limit: weak statistical generalisation; analytic generalisation instead

Common misconceptions

What people often get wrong

Often heard: A case study is just an anecdote and not a rigorous research method.

Actually: A well-designed case study uses defined boundaries, multiple evidence sources and triangulation to produce systematic, defensible findings — it is an established method, not an informal story.

Often heard: Case studies are always qualitative.

Actually: Case studies can be qualitative, quantitative or mixed. Qualitative case studies are most common in social research, but the method is defined by depth and bounded focus, not by data type.

Often heard: Case study findings cannot be generalised at all.

Actually: They support analytic or theoretical generalisation — to concepts and theory — rather than statistical generalisation to populations, which is a legitimate and valuable form of inference.

Going deeper