Anomalous Readings (Edexcel International A Level Physics)

Revision Note

Katie M


Katie M



Anomalous Readings

  • Experimental errors (also known as operator errors or ‘one off’ errors) will affect the results of an experiment and can produce anomalies
    • These anomalies should be identified during the evaluation of results and before drawing conclusions

  • Anomalies can be identified by looking for results or data points on a graph that do not fit with the trend or with other repeat readings carried out during the experiment
    • These anomalous results will show a larger difference from the mean than the rest of the results (a result is often taken to be anomalous if it differs from the mean result by more than 10%)
  • The results or ‘data’ collected from an experiment can be made more reliable if the experiment is repeated several times and anomalies are removed
    • This, in turn, allows more valid conclusions to be drawn

  • Anomalous results are always inconsistent with other readings e.g., a point that is not on the line of best fit of a graph

Identify-anomalies-on-graphs, IGCSE & GCSE Chemistry revision notes

Identifying an anomalous result from a graph

  • If an anomaly occurs in the experiment:
    • Ignore this value when calculating the mean
    • Repeat this measurement

Worked example

A student achieves a set of repeat readings for the current through a bulb.

2.5 mA 2.8 mA 6.1 mA 2.0 mA 2.3 mA

Calculate the mean current through the bulb.

1. Identify the anomalous result

    • The only result that doesn't fit with the rest of the data is 6.1 mA
    • This can be ignored when calculating the mean

2. Calculate the mean current

Mean current = fraction numerator 2.5 space plus space 2.8 space plus space 2.0 space plus thin space 2.3 over denominator 4 end fraction  = 2.4 mA

Exam Tip

When calculating the mean of some repeat readings for data given in your practical paper, always ignore any anomalous readings that are inconsistent when calculating the mean.

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Katie M

Author: Katie M

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.