Question
Explain how the interquartile range (IQR) can be used to interpret variability in fieldwork data, using an example from either a river or urban study. [4]
Mark scheme (4 marks) — levelled:
- Level 1 (1–2 marks): Basic definition. 'IQR is Q3 minus Q1' or 'shows the middle 50% of data'. No applied example.
- Level 2 (3–4 marks): Definition PLUS applied geographical example. E.g. 'In a river study, an IQR of 0.25 m/s in velocity readings on the outside bend versus 0.08 m/s on the inside bend shows greater variability where helicoidal flow causes turbulence. The IQR is preferable to the range because it excludes the two extreme readings caused by a momentary obstruction in the channel.'
- Credit reference to box-and-whisker plots, outlier identification (1.5 × IQR rule), or comparison between sites.
4 marks · take your time before peeking.
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Generated by TopMyGrade AI · cross-check official sources before relying on the mark-scheme phrasing.