Quantitative and Qualitative Data

🔬 Quantitative and Qualitative Data

Beyond primary and secondary, data divides into quantitative (numerical, measurable) and qualitative (descriptive, observational). Both types have a role, and using only one type is a common evaluation weakness.

Quantitative Data

Quantitative data takes the form of numbers that can be measured, compared, and analysed statistically. It allows you to identify patterns and test hypotheses with statistical confidence.

• River velocity measured in metres per second (m/s)
• Pebble long-axis length measured in millimetres
• Pedestrian count: number of people per 5-minute observation period
• Environmental quality index score (e.g., 1–5 scale for each indicator)
• Temperature in degrees Celsius
• Sediment depth in centimetres

Qualitative Data

Qualitative data describes characteristics, opinions, or observations that cannot easily be reduced to a number. It adds context, explanation, and human insight to patterns identified in quantitative data.

• Photographs of different sites along a transect
• Annotated field sketches of a river meander
• Open-ended questionnaire responses ("What do you like / dislike about this area?")
• Observer notes on land use type or building condition
• Interview transcripts with local residents

The strongest investigations use both types in combination — quantitative data to identify what the pattern is, and qualitative data to explain why it exists. For example, a pedestrian count (quantitative) might reveal a sharp drop in footfall at a particular point; a photograph and field sketch (qualitative) might show that the change corresponds with the end of the main retail zone and the beginning of a residential area.