Theory
Calculating percentage uncertainty
An absolute uncertainty tells how much the measurement can differ in ordinary units.
With a percentage uncertainty, you compare that difference with the size of the measured value.
Use: percentage uncertainty = absolute uncertainty : measured value × 100%.
- Read the measured value and absolute uncertaintyFind the measured value and absolute uncertainty in the problem.
- Divide the uncertainty by the measured valueWork out the intermediate step using the values from the problem.
- Convert to percentagesWork out the intermediate step using the values from the problem.
A length is 10,1 cm with absolute uncertainty 0,3 cm. Calculate the percentage uncertainty.
- Read the measured value and absolute uncertaintyMeasured value = 10,1. Absolute uncertainty = 0,3.
- Divide the uncertainty by the measured value0,3 ÷ 10,1 = 0,03.
- Convert to percentages0,03 × 100 = 2,9703%.