Measurement and Data Interpretation
Measurement and Data Interpretation
This domain tests unit conversion, reading scales and tables, and summarising data with mean, median, mode and range. Expect questions that mix a conversion with a data calculation, such as comparing times or costs.
Core rules
- Metric conversions: 1 km = 1000 m; 1 m = 100 cm; 1 cm = 10 mm; 1 kg = 1000 g; 1 L = 1000 mL. For time, 1 hour = 60 minutes; 1 minute = 60 seconds.
- Mean = total of values ÷ number of values. Median = middle value after ordering; if there is an even count, average the two middle values. Mode = most frequent value. Range = largest − smallest.
- When reading a graph or table, check the axis scale and units. A value halfway between two marked ticks needs interpolation.
- Keep units consistent before adding or comparing; convert to the same unit first.
Worked example
Find the mean, median, mode and range of 4, 7, 7, 9, 13. Total = 4 + 7 + 7 + 9 + 13 = 40; mean = 40 ÷ 5 = 8. Ordered data: 4, 7, 7, 9, 13; median = 7. Mode = 7 (it appears twice). Range = 13 − 4 = 9.
Traps
Finding the median before ordering the data; dividing by the wrong count; mixing grams and kilograms; reading a bar chart from the top of the bar rather than the scale; and forgetting that range is a single number, not a pair.