Sample size and anomalous results

An anomalous result is a result that doesn’t fit in with the pattern of the other results. It is an anomaly.

Taking many repeat measurements or having a large sample size to analyse will improve accuracy. Anomalous results can be easily spotted in the data and discarded, leading to a more accurate calculation of the mean.

Look at the following six results taken by a student.

0.63, 0.71, 0.64, 0.69, 1.20, 0.67

The anomalous result is 1.20. It is too high compared to the other results.


Calculate the mean of the results without the anomalous reading.

The mean of the remaining five results is (0.63 + 0.71 + 0.64 + 0.69 + 0.67) ÷ 5 = 0.668 rounded up to 0.67.

Slow motion cameras

Sometimes something can be moving too quickly for us to accurately take a reading.

A bouncing ball can be filmed with a slow motion camera bouncing up against a scale to see the height it bounces to.

This will improve the accuracy of the measurement.