Market Research Methods and Data Collection
This domain tests your grasp of research design, sampling, and data quality. Distinguish primary research (collected for your specific question) from secondary research (existing data), and qualitative (exploratory, small-n, "why") from quantitative (statistical, large-n, "how many").
Know common methods: surveys, interviews, focus groups, ethnography/observation, A/B tests, and web analytics as observational data. Understand sampling: probability vs. non-probability, random, stratified, and convenience sampling. Recognize that convenience samples limit generalizability. Grasp validity (measuring what you intend) versus reliability (consistency of measurement).
Traps: questions that confuse correlation with causation-observational data (like analytics) shows association, not proof. Another trap is sampling bias: a survey promoted only to existing customers cannot represent the broader market. Watch for leading or double-barreled survey questions (asking two things at once), which invalidate results. Also distinguish response bias from non-response bias.
Worked rule of thumb: Before trusting a finding, ask three questions-Was the sample representative? Was the instrument neutral? Does the design support a causal claim? If a scenario claims causation from a simple before/after comparison with no control group, the correct critique is that confounders weren't controlled.
For qualitative work, sample size is judged by saturation (new themes stop emerging), not a fixed number. For quantitative work, margin of error shrinks with larger samples but is also affected by population size and confidence level.