Accuracy and Uncertainty
Accuracy is how close a measurement is to the true value, and uncertainty states the range in which the true value probably lies.
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Accuracy is how close a measurement is to the true value, and uncertainty states the range in which the true value probably lies.
- Precise results are close to each other
- Accurate results are close to the true value
- Report values with an uncertainty
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Accuracy and Uncertainty?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Accuracy and Uncertainty. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain Accuracy and Uncertainty in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Accuracy and Uncertainty explains how the physical world behaves, from sport and transport to electricity and medicine.
Accuracy and Uncertainty in detail
Accuracy describes how close a measurement is to the true value, while precision describes how closely repeated measurements agree with each other. Random errors scatter results above and below the true value and can be reduced by averaging, while systematic errors, such as a zero error, shift all results in one direction.
Uncertainty gives a range within which the true value is expected to lie, such as 12.0 ± 0.2 cm. The percentage uncertainty is uncertainty ÷ value × 100. Reporting uncertainty lets you judge whether two results really differ and how reliable a conclusion is.
How the interactive helps you understand Accuracy and Uncertainty
Watch the bar chart in the interactive. Use any sliders or buttons it offers to change the values and see how the bar chart responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Accuracy and Uncertainty.
Real-life uses and examples
- Predict what a ball, car or circuit will do with Accuracy and Uncertainty before you do the calculation.
- Explain everyday devices, such as brakes, lifts or chargers, using Accuracy and Uncertainty.
- Use Accuracy and Uncertainty to make sense of a practical and its results.
Common mistakes to avoid
- Mixing up Accuracy and Uncertainty with a related quantity that has different units.
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Accuracy and Uncertainty
What is Accuracy and Uncertainty?
Accuracy is how close a measurement is to the true value, and uncertainty states the range in which the true value probably lies.
What are the most important points about Accuracy and Uncertainty?
The main points are: Precise results are close to each other; Accurate results are close to the true value; Report values with an uncertainty.
Why is Accuracy and Uncertainty useful?
Understanding Accuracy and Uncertainty explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise Accuracy and Uncertainty?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Accuracy and Uncertainty?
Related topics in Physics include Speed and Velocity, Free Fall and Gravity, Newton's Second Law.