Match each source to the question it can answer, then compare sources that measure different parts of the issue.
Primary data are collected for your investigation: interviews, questionnaires, measurements or systematic observations. Use consistent definitions and recording sheets. Record units, dates, times and location IDs so you can match observations correctly.
Secondary data already exist, including census tables, rainfall records and images. Check their collector, purpose, date, definitions and spatial resolution: a district average cannot describe every street.
Geospatial data attach information to locations. Use a geographical information system (GIS) to measure routes or compare services. OneMap provides authoritative Singapore mapping; check routes for barriers on the ground and retain the map's date and scale.
Check regional classifications before combining datasets. The syllabus uses seven World Bank macro-regions: East Asia and Pacific (Singapore, Indonesia); Europe and Central Asia (Germany); Latin America and the Caribbean (Brazil); Middle East and North Africa (Morocco); North America (United States); South Asia (India); and Sub-Saharan Africa (Kenya). Compare within as well as between regions: averages hide differences among countries and neighbourhoods.
Step by step
List the evidence needed
Separate physical conditions, behaviour and lived experience.
Collect consistently
Use IDs, agreed categories and stated units at every site.
Check compatibility
Compare dates, boundaries and definitions before combining sources.
Worked example: One route, three pieces of evidence
A map gives an invented clinic route as 300 m. An audit records two steps and no shade; a resident explains that these make the walk difficult. The sources answer different questions: how far, which barriers and how they affect the user. Match them by route and date. A short distance alone would miss the access problem.
Watch out for this
A digital map is automatically more accurate than field observations.
Accuracy depends on date, resolution, method and purpose. Check both sources against the feature you need to measure.
Check your understanding
A 2015 map and a 2026 survey disagree about bus access. What should you check first?
- Whether routes or definitions changed between the dates.
- Whether the map looks more professional.
- Which result supports the hypothesis.