Analysing data turns raw measurements into evidence. Calculate a mean for each set of repeats, excluding clear anomalies with a stated reason. Use the range to estimate uncertainty, and present results to a sensible number of significant figures, usually matching the least precise measurement.
Look for patterns using graphs; where uncertainty is shown, check whether the error bars of different points overlap. If they overlap a lot, the difference between those results may not be real. Calculations such as rates, percentages and gradients should carry units throughout.
Worked example
Repeats 2.4, 2.6, 2.5 and 3.9 s. Give the mean and its uncertainty without the anomaly.
- 3.9 s is anomalous and is excluded.
- Mean = (2.4 + 2.6 + 2.5) ÷ 3 = 2.5 s.
Answer:Range 0.2 s, so 2.5 ± 0.1 s.
Key words
- significant figures
- the digits that carry meaning in a value
- error bars
- lines showing the uncertainty of a point
- raw data
- measurements before processing
- processed data
- means, rates or other calculations
Practise this
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