3.14 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

Identifying an anomalous result from a graph

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

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 =   = 2.4 mA