Errors in measurement
A standard method from Number and algebra basics: the steps and worked examples.
Steps
- Maximum absolute error = ½ × the smallest unit of measurement.
- Relative error = maximum absolute error ÷ measured value.
- Percentage error = relative error × 100%.
- The true value lies between (measured − max error) and (measured + max error).
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Worked examples
Example 1: Errors in measurement: a rope is measured as 25 cm, correct to the nearest cm.
Maximum absolute error = 0.5 cm. Relative error = 0.5 ÷ 25 = 0.02. Percentage error = 2%. The true length lies between 24.5 cm and 25.5 cm.
For the whole topic, read Number and algebra basics: key points, common mistakes and how the DSE tests it.