Percent uncertainty

Definition

Percent uncertainty is a measure of the relative size of the uncertainty in a measurement compared to the size of the measurement itself, expressed as a percentage. It helps assess the precision and accuracy of measurements.

5 Must Know Facts For Your Next Test

1. Percent uncertainty is calculated using the formula $\text{percent uncertainty} = \left( \frac{\text{absolute uncertainty}}{\text{measured value}} \right) \times 100$.
2. Absolute uncertainty is the margin of error in a measurement and can be derived from instrument precision or repeated measurements.
3. A lower percent uncertainty indicates higher precision in measurements.
4. Significant figures play a crucial role in determining both absolute and percent uncertainties.
5. When combining measurements, each with their own uncertainties, propagate these uncertainties to determine the overall percent uncertainty.

Review Questions

• How do you calculate percent uncertainty from absolute uncertainty and measured value?
• What does a lower percent uncertainty imply about a measurement's precision?
• Why are significant figures important when calculating uncertainties?

Related terms

Absolute Uncertainty: The margin of error associated with a measurement, typically given as a fixed quantity.

Significant Figures: The number of digits in a number that contribute to its accuracy, including all certain digits and one uncertain digit.

Precision: The degree to which repeated measurements under unchanged conditions show the same results.