BRAINCAKECombining Uncertainties
When a result is calculated from several measured quantities, their uncertainties combine. AQA uses three rules.
1. Adding or subtracting: add the absolute uncertainties. Two lengths of 12.3 ± 0.1 cm and 4.5 ± 0.1 cm have a difference of 7.8 ± 0.2 cm. The uncertainties still add when you subtract.
2. Multiplying or dividing: add the percentage uncertainties.
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Key terms in this lesson
- percentage uncertainty
- The absolute uncertainty in a measurement divided by the measured value and multiplied by 100%, giving the uncertainty as a percentage.
More in Measurements and Errors
- Converting Units
- Random and Systematic Errors
- Precision, Repeatability and Reproducibility
- Resolution and Accuracy
- Absolute, Fractional and Percentage Uncertainty
- Uncertainties on Graphs
- Uncertainty in a Gradient
- Estimation and Orders of Magnitude
All 12 lessons in Measurements and Errors · All AQA AS-level Physics topics