Explain why a method was chosen

Question (6 marks): A student investigated traffic volumes at five points along a route in Cardiff. Explain why a proportional symbol map would be a suitable presentation method.

Mark scheme (Levels):

• Level 1 (1–2): Basic — symbols are bigger for more traffic.
• Level 2 (3–4): Clear — proportional symbols (circles scaled by area) located at each survey point allow simultaneous display of location and magnitude; reader can compare sites visually.
• Level 3 (5–6): Detailed — accurate use of terminology (spatial, quantitative); recognises that area, not radius, must be proportional to value to avoid visual exaggeration; identifies a limitation (overlap at clustered points; precise values harder to read than a bar chart) and suggests a located bar chart as a complement.