# A student measures the resistance of a resistor five times using an ohmmeter. His results are: 47 Ω, 52 Ω, 49 Ω, 48 Ω, and 51 Ω. Describe how the student should process these results to obtain a reliable value for the resistance, and explain what the range of results tells him about the precision of his measurements.

> AQA A-Level Physics (7408) — 3.1.2 Limitations of Physical Measurements · Describe · 5 marks

## Mark scheme (5 marks)

1. Identifies that the student should calculate a mean (average) of the five readings
2. States that all five readings should be included in the mean (no reading is anomalous / there is no outlier to exclude)
3. Links a smaller range to greater precision (or states the range indicates how spread out / consistent the readings are)
4. States or calculates that the range here is 5 Ω (52 − 47) indicating the measurements are not very precise
5. Distinguishes precision from accuracy — precision is about repeatability / consistency of readings, not about closeness to the true value

## Key terms

- [range](https://www.gradenine.co.uk/glossary/range)
- [precision](https://www.gradenine.co.uk/glossary/precision)

## Related

- [Revision notes for AQA A-Level Physics (7408)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-measures-the-resistance-of-641ab37b) · Published by Druglandscape Ltd.