In one line: A case study looks at one person, one group or one event in great detail, usually over a long time.
A doctor meets a patient whose problem appears in no textbook.
She cannot test a hundred people like him, because there are none. So she studies him: she talks to him, tests him, watches him and reads his records, for months.
That is a case study. It gives up breadth to gain depth.
What a case can be
- A person: a patient with a rare kind of memory loss.
- A group: a family, a class, a sports team.
- An event or a place: a school closing down, a town after a flood.
In psychology a case study is a research method, but it has no tool of its own. It collects its data through other methods: interviews, observations and tests.
Remember: One case. Many methods. A long time.
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Key idea: Case studies suit cases that are rare, complex or impossible to set up.
Take Dan, who hit his head in a cycling accident. He remembers his childhood clearly, but he forgets every new thing within a few minutes.
Four features
Rare cases
The case is too unusual for any other method.
There are not enough people like Dan for an experiment, and nobody could ethically cause such an injury.
Rich data
Several methods are combined: interviews with Dan and his family, memory tests, observation at home.
That gives both words (qualitative data) and numbers (quantitative data, such as test scores).
Real context
Dan is studied in his own life, not in a set-up situation.
The researcher sees how the memory loss affects his job, his family and his day.
Over time
The case is followed for months or years.
A study that measures the same people again and again over a long period is longitudinal.
Rare · Rich · Real · Over time
What one case can do: One striking case can change a theory.
If Dan can learn a new card trick but cannot remember the lesson, memory must have more than one system. No large study was needed to show that it is possible.
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Key idea: A case study uses several sources on the same case, so each one can check the others.
Dan's own account is one source. But his memory is the very thing that is damaged, so his account cannot be trusted alone.
Using more than one source to study the same thing is called triangulation.
Four types of triangulation
Method triangulation
Different methods on the same case.
Here: interviews, memory tests and observation of Dan at home.
Data triangulation
Different sources of data, or the same source at different times.
Here: Dan, his sister, his employer and his hospital records.
Researcher triangulation
More than one researcher collects or analyses the data, and they compare what they found.
Here: two psychologists read the interview notes separately.
Theory triangulation
The findings are read through more than one theory.
Here: one explanation based on brain damage and one based on Dan's stress since the accident.
Method · Data · Researcher · Theory
When different sources agree, the findings are more credible. When they disagree, the researcher has found something that needs a closer look.
Exam tip: Name the type.
"They used triangulation" is vague. "Method triangulation: interviews, memory tests and observation" is precise.
Key idea: A case study gives the deepest picture of one case. The price is that it may only be true of that case.
Strengths
- Rich detail about one case
- Reaches rare cases that could not be set up
- Seen in its real-life setting
- Gives ideas for research, and can challenge a theory
Limits
- Cannot be repeated to check it
- Cannot be generalised to everyone
- No control, so no cause and effect
- Researcher bias; anonymity is hard to keep
A study that cannot be repeated has low reliability.
And its findings are not generalised to everyone. They may be transferred to cases that are similar: another patient with the same injury.
Watch out: One case is a clue, not a law.
Dan shows what can happen after this injury. He cannot show what happens to everyone.
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How this is asked: A case study is not something a class can run as a practical, so you are not asked to describe or design one. You are asked to compare it with the method your class did use, for 6 marks.
Your class practicals
- Your class runs four small studies of its own, called class practicals.
- They are an experiment, an interview, an observation and a survey.
- Paper 2 asks about the ones your class ran.
- Keep a short note of each: aim, what you did, who took part, what you found, and the ethics.
The answer pattern
- Two or three similarities, each starting with "Both".
- Two or three differences, each using "whereas".
- Your own practical in every paragraph.
The trap: two descriptions: A paragraph about your practical followed by a paragraph about case studies compares nothing.
Put both methods in the same sentence.
Your class practical was an interview. Each student interviewed one classmate for ten minutes about how they revise for tests. Compare and contrast the research methodology of the interview used in your class practical with the research methodology of a case study.
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