Topic Three (1.3): Errors and Accuracy
Introduction
Science is built on experimental observation, but no measurement is completely accurate. So, all our observations are subject to a level of uncertainty. We don’t know the true value precisely, but we should always have a reliable idea how far our observations may be from the truth. Thus, understanding this area is vital for good science, and it requires strong skills in careful planning, attention to detail, careful procedure and checking, and good mathematical understanding and skills. Unfortunately, the way language is used (even in some teaching materials) encourages confusion, but if you go through the resources in this topic carefully, you should be able to understand quite easily and clearly. Take your time to learn this thoroughly; it will be time very well spent!
An accurate darts player can hit the bullseye. But a precise and accurate darts player can hit the bullseye with all three darts. There will be a lot of uncertainty in a darts player who has a wide spread of throws, a higher degree of error.
Tasks
Complete the following:
READ – Measurement, Accuracy and Uncertainty Download READ – Measurement, Accuracy and Uncertainty
- Make some brief notes in your own words to summarise this information. Use the following videos to help.
- Keep referring back to this document and your notes, particularly when you prepare for each of your Core Practicals.
WATCH – Precision, Accuracy and Uncertainty in Measurement in Chemistry (YouTube) Links to an external site. (But applies to Physics too)
WATCH – Uncertainty Estimates for Physics Labs (YouTube) Links to an external site.
WATCH – Experimental Uncertainties (YouTube) Links to an external site.
WATCH – Errors, Percentage Uncertainties and Compound Errors (YouTube) Links to an external site.
WATCH – Percentage Uncertainty in a Gradient (YouTube) Links to an external site.
Top Tips
Make sure that you understand the following key points:
- Check if you can clearly explain to someone else the definitions and distinctions between these things:
- Experimental error, and human error.
- Random and systematic error.
- Accuracy and precision, of an experimental reading.
- Precision of a number, of a single instrument reading, and of a collection of instrument readings.
- How to minimise parallax and meniscus errors.
- Typical accuracy values for common measuring equipment.
- Accuracy is how close to the true value the measurement is.
- Precision is how closely grouped the repeated results are.
- The summary you make from the document ‘Measurement, Accuracy and Uncertainty’ will be extremely useful throughout the course. Keep those notes at the front of your folder along with your data book of equations, and notes about SI prefixes and powers of ten.
Key Terms
Add the following key terms with definitions to your word list:
- Accuracy
- Precision
- Uncertainty
- Error
- Repeatable
- Reliable