Questionnaires, interviews and case studies
Choose open or closed questions, distinguish written and verbal data collection and explain triangulation in a case study.
Original teaching mapped to Cambridge IGCSE Psychology 0266 Version 3 for 2027–2029. The course is independent study support, not Cambridge material, an official mark scheme or an awarded grade. Named-study notes summarise the required findings; candidates are not expected to evaluate named studies. Self-check practice is not official grading, a timed Paper 1/2 simulator or teacher review.
Before you begin
- Use the Version 3 syllabus and confirm availability in your administrative zone with Cambridge and your school. Both papers are compulsory. The updated named-study summaries are required context; full original research articles are not required.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Before questionnaires, interviews and case studies, which approach is most useful?
What you will learn
- Describe questionnaires and interviews within syllabus boundaries
- Distinguish open and closed questions
- Describe a case study and its data sources
- Explain triangulation and apply methods to a scenario
Questionnaires and interviews collect answers in different formats
A questionnaire collects written responses; an interview collects verbal responses. Open questions invite detailed answers in a participant’s own words. Closed questions provide a fixed set of response choices. Match the format to the information needed: fixed choices are easier to compare; open answers can reveal unanticipated detail.
A case study investigates one case in depth
A case may be a single person, group or event. A researcher can combine tests, tasks, observations, questionnaires and interviews. Triangulation means comparing evidence from different methods or sources to build a fuller account.
Use the syllabus boundary deliberately
Postal questionnaire methods and types of interview (structured, semi-structured, unstructured, telephone, face-to-face) are not required content. Focus on written versus verbal responses and open versus closed questions.
Pause and explain
Which response best shows understanding of questionnaires, interviews and case studies?
Worked example
A researcher wants participants to describe how they felt in their own words. Which question format suits this aim?
Show the worked solution
- The aim needs detailed responses.
- No fixed answer set should constrain the response.
- An open question is appropriate.
Answer An open question invites a detailed answer in the participant’s own words.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A survey asks ‘How often do you revise: never, sometimes, often, always?’ Is this open or closed?
Give me a hint
The answer choices are supplied.
Compare my reasoning
- The researcher gives fixed options.
- Participants choose among them.
- This is a closed question.
Closed question.
Look for these in your work
- Notes fixed options
- Explains the response format
- Names the type
A researcher follows one learner’s memory difficulties using tasks, observations and interviews. Which method is this, and what is triangulated?
Give me a hint
Consider both the focus and the sources.
Compare my reasoning
- The investigation focuses in depth on one person.
- It uses multiple kinds of evidence.
- This is a case study using triangulation.
A case study; evidence from tasks, observations and interviews is triangulated.
Look for these in your work
- Identifies one case
- Names several sources
- Explains triangulation
A school wants to compare stress ratings across 200 students, then understand one student’s experience in depth. Suggest a method for each aim.
Give me a hint
Choose comparable data first, then richer multi-source detail.
Compare my reasoning
- A closed questionnaire can provide a common response scale across many students.
- A case study can combine several methods for one student.
- The method should match whether the aim is breadth or depth.
Use a closed questionnaire for broad comparison and a case study for an in-depth account.
Look for these in your work
- Matches scale to questionnaire
- Matches depth to case study
- Justifies the choices
Common mistakes
- Calling an interview a written questionnaire.
- Assuming open questions make answers directly comparable.
- Adding excluded interview subtypes as required syllabus knowledge.
What can you explain now?
What is triangulation?
Compare with the explanation
Combining evidence from different methods or sources
Using more than one method can provide a fuller view of a case.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
How do open/closed questions, interviews and case-study triangulation serve different research aims?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.