Choosing the right data collection method is one of the most consequential decisions in your Extended Investigation. The method must align with your research question — using the wrong method can produce data that simply cannot answer what you are asking.
| Feature | Quantitative | Qualitative |
|---|---|---|
| Data type | Numbers, measurements | Words, images, themes |
| Goal | Measure, quantify, generalise | Understand, interpret, explore |
| Sample size | Usually large | Usually small |
| Question type | “How much?”, “How many?”, “Is there a relationship?” | “Why?”, “How?”, “What does this mean?” |
| Analysis | Statistical | Thematic, interpretive |
| Researcher role | Aims for objectivity | Acknowledges subjectivity |
KEY TAKEAWAY: Neither quantitative nor qualitative is inherently superior. The best method is the one that best fits your research question. Many strong investigations use a mixed-methods approach, combining both.
Strengths: Fast, cheap, can gather data from large samples, easy to analyse statistically, replicable.
Weaknesses: Superficial — cannot capture complexity; responses may be dishonest; wording can bias results; cannot follow up unexpected responses.
Strengths: Can establish cause-and-effect relationships (highest level of causal evidence); controlled variables reduce confounding factors.
Weaknesses: Artificial conditions may not reflect real life (low ecological validity); many research questions are not experimentally testable for ethical or practical reasons.
Strengths: Records actual behaviour rather than self-report; can be standardised for reliability.
Weaknesses: Observer effect (people behave differently when watched); time-intensive; limited to observable behaviour.
Strengths: Non-reactive (documents exist independently of the researcher); can analyse historical data.
Weaknesses: Documents may be incomplete, biased or not representative.
Strengths: Rich, detailed data; can explore unexpected themes; flexible to follow participant responses.
Weaknesses: Time-intensive; small sample sizes limit generalisability; susceptible to interviewer bias; analysis is complex.
Strengths: Capture group dynamics and shared social meanings; efficient (multiple participants at once).
Weaknesses: Dominant voices can skew discussion; participants may conform to group opinion; less useful for sensitive topics.
Strengths: Can gather qualitative data at larger scale than interviews.
Weaknesses: Responses may be brief or superficial; requires interpretive coding, which introduces researcher subjectivity.
Strengths: Deep, contextual understanding of a social environment.
Weaknesses: Extremely time-consuming; researcher presence can alter the environment; difficult to generalise.
EXAM TIP: When asked to evaluate a method, always consider both the general strengths/weaknesses and how they apply specifically to the research question in the scenario. A survey that works for measuring preferences fails for measuring complex emotional experiences.
Using both quantitative and qualitative data in a single investigation:
- Sequential: Qualitative phase generates hypotheses → quantitative phase tests them (or vice versa)
- Concurrent: Both types collected simultaneously and compared
- Embedded: One type supports or contextualises the other
Strengths: Triangulation — if qualitative and quantitative results converge, confidence in findings increases.
Weaknesses: More complex to manage, analyse and write up; requires competence in both approaches.
| Research Question Type | Appropriate Method |
|---|---|
| “Does X cause Y?” | Experiment or controlled quasi-experiment |
| “How common is X?” | Survey with large sample |
| “Why do people do X?” | Interviews or focus groups |
| “What is the relationship between X and Y?” | Correlational survey (quantitative) |
| “What is the lived experience of X?” | Interviews, ethnography |
| “How has X changed over time?” | Document analysis, longitudinal survey |
COMMON MISTAKE: Choosing a method because it is easiest, not because it fits the question. A survey cannot tell you why people behave a certain way — only that they do. If your question asks “why,” you need qualitative methods.
REMEMBER: In your written rationale and report, you must justify your choice of methods. This means explaining why your chosen method is appropriate for your question, not just describing what it is.
