Two technicians used the same method to measure the time taken for a reaction mixture to turn cloudy.
Technician P repeated the measurement five times.
| Repeat | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Time in s | 42.0 | 42.2 | 42.4 | 47.8 | 42.2 |
Technician Q's result was 42.2±0.4 s42.2 \pm 0.4\ \text{s}42.2±0.4 s.
Calculate the mean time and the estimated uncertainty for technician P's results.
Give your answer in the form mean ± uncertainty.
Which technician's mean can be trusted more?
Give a reason for your answer.
95 exam-style questions on AQA GCSE Chemistry 3.1 Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations, covering 3.1.1 Conservation of mass and balanced chemical equations, 3.1.2 Relative formula mass, 3.1.3 Mass changes when a reactant or product is a gas, and 3.1.4 Chemical measurements. Each one has a worked solution and a mark scheme showing where the marks go.