What a case study is
Definition
Case study
An in-depth investigation of a single person, group or event, usually combining several methods to gather rich, detailed data.
- A case study is a detailed investigation of one person, one small group or one event.
- It goes deep into a single case rather than skimming across many, so the sample is tiny and is often just one person.
- Most of what it produces is qualitative data, a written account of what the person did, said and experienced.
Example
- Suppose a woman loses the ability to form new memories after an illness, and a psychologist follows her for two years.
- They interview her and her family, set her memory tasks, read her medical notes and watch how she manages at home.
- No experiment could ever have created that situation, and no questionnaire could capture what it is like to live inside it.
How the data is gathered
- A case study is not one technique but several used on the same case.
- Interviews, observations, questionnaires, tests and existing records can all feed into the account.
- When several different sources point the same way, you can be more confident the account is accurate.
Strengths
- It reaches cases that could not be created, since rare conditions, unusual injuries and one-off events could never be set up deliberately.
- The detail is unmatched, because following one case over months captures personal detail that a survey of a thousand people would flatten into an average.
Weaknesses
Definition
Generalisability
How far the findings from the people studied can be applied to other people beyond the study.
- Generalisability is poor, because a finding from one unusual person may say nothing about anybody else, and the unique case cannot be repeated to check.
- Researcher bias creeps in, because working closely with one person for months makes it easy to read the evidence in the way you already expected.
Common Mistake
- Do not write that a case study proves a theory, because one case can support or challenge an idea but never settle it.
- Do not treat a case study as an experiment, because nobody manipulates an independent variable.
When to choose a case study
- Choose it when the case is rare and there is simply no other way to study it.
- Choose it when you want to understand a whole life or a whole event rather than one narrow measurement taken from it.
- Choose it when watching how something unfolds over time matters more than counting how often it happens.
- Choose another method when you need a finding that applies to people in general.
Turning this into marks
- Name the depth, the single case and the use of more than one technique on it.
- Say generalisability or researcher bias and then finish the thought with its consequence.
- The mark most often lost is balance, so set the richness of the data against the difficulty of applying it to anyone else.
Self review
- What is a case study, and what kind of data does it mostly produce?
- Explain why a case study is hard to generalise from.
- Give a research question a case study would suit better than an experiment, and say why.
