Explain how sampling strategy affects data reliability

Question (6 marks): Explain how the choice of sampling strategy can affect the reliability of primary data collected during fieldwork. Refer to at least two sampling methods.

Mark scheme (6 marks — levels-based):

Level 3 (5–6 marks): Detailed explanation of two or more sampling strategies with clear link to reliability. Uses correct terminology (systematic, stratified, random, pragmatic). Recognises bias and representativeness. Example: Systematic sampling along a beach transect (every 10 m) ensures even spatial coverage and reduces investigator bias, increasing reliability of a sediment-size profile. Stratified sampling of questionnaire respondents by age group ensures sub-populations are proportionally represented, preventing skew if only retirees are available mid-week.

Level 2 (3–4 marks): Identifies two strategies with some explanation of effect on reliability. May lack precise terminology or full development.

Level 1 (1–2 marks): Names a sampling method with limited or no link to reliability.

0 marks: No relevant content.

Indicative methods: random (unbiased but may cluster), systematic (even coverage but may miss anomalies), stratified (representative but requires prior knowledge of sub-groups), pragmatic/opportunistic (convenient but biased).