Identifying and explaining anomalies

Describe how a student should identify and respond to anomalous results when interpreting fieldwork data. [6]

Mark scheme (6 marks) — levelled:

• Level 1 (1–2): Generic statement that anomalies are 'odd values' or 'unusual results'; one method named (e.g. 'circle them on a graph').
• Level 2 (3–4): Two clear methods of identification — visual inspection of scatter graph / line graph, or using the 1.5 × IQR rule on a box plot, or values more than 2 standard deviations from the mean. Brief reference to causes (instrument error, atypical conditions).
• Level 3 (5–6): Detailed sequence: (1) plot data and visually identify outliers; (2) check raw data record for transcription or measurement error; (3) consider geographical reasons — e.g. a velocity reading taken downstream of a fallen branch causing turbulence; (4) decide whether to retain, exclude with justification, or repeat; (5) recalculate descriptive statistics to test sensitivity. Reference to honesty / academic integrity in reporting anomalies rather than discarding silently.