Number of Readings (Edexcel International A Level Physics)

Number of Readings

• When recording data from an experiment, it is important to take a suitable number of readings

  • Repeat readings should also be taken where possible

• An example of a table of results with an appropriate number of readings is:

Example Table of Results with a good number of readings

• A good number of repeats is between 3 - 5 times

  • In the diagram, there are 3 repeats of each reading

• Multiple measurements increase precision

  • It also makes your measurements more reliable

• They also increase confidence in the experimental data

  • Making the same measurement multiple times then taking an average decreases the uncertainty in the value

  • The absolute uncertainty in repeat readings is equal to ± half the range of readings

• It also checks how reproducible the measurements are, so the results are not just from luck or a fluke

• Results should be recorded to the resolution of the measuring instrument which means there will be a consistent number of decimal places for the readings for any one variable

  • They should be recorded to a consistent number of significant figures, which is usually 3, as this is what we can usually confidently plot on a graph

  • For example, readings for a micrometer should be to two decimal places (since its resolution is 0.01 mm) whilst for a ruler, only 1 decimal place would be enough when measuring in cm, or 2 decimal places when measuring in metres (since its resolution 0.1 cm / 0.01 m / 1 mm)