Processing data


The best way to display collected data is in a table. This helps to organise your data collection.

The following are good guidelines when presenting results in tables:

  • if drawing a table by hand use a ruler and a pencil
  • column headings should show quantity and unit
  • independent variable in the first column and dependent variables in columns to the right
  • all results for a particular quantity should be recorded to the same number of decimal places
  • no units in the body of the table


A student has been investigating how the time for ten swings of a pendulum varies with length. They record the following results:

The table measures lengths against the time taken for ten swings

Length (cm)Attempt 1 (s)Attempt 2 (s)Attempt 3 (s)Average time for ten swings (s)

Significant figures

When doing calculations with measured answers, the answer should have the same number of significant figures as the measured value.

When rounding a number that has more significant figures than are justified, round up if the last figure is between 5 and 9 inclusive, if it is between 0 and 4 inclusive round down.

For example, the number 3.5099 rounded to:

  • 4 significant figures is 3.510
  • 3 significant figures is 3.51
  • 2 significant figures is 3.5
  • 1 significant figure is 4

Charts and graphs


Charts are a way to display data after it has been collected.

Discrete data can only have certain values and are shown using a bar chart. This can help to show any patterns.

A pie chart shows a category compared with the whole. For example, the percentage of each energy source used in the UK can be shown using a pie chart.

Pie chart showing global energy consumption in 2014.


Continuous data can take any value in a given range. It includes time, mass and length.

Continuous data should be presented on a line graph. Line graphs are particularly useful in helping to spot any trends or patterns in the data. For example, the relationship between current and voltage for a resistor.

Graph plotting voltage against current for a fixed resistor. Line is directly proportional.

The following is best practice when drawing graphs:

  • use a ruler and pencil to draw the axis
  • label the axis with the quantity and the unit it is measured in
  • the independent variable should be plotted on the X-axis and the dependent variable should be plotted on the Y-axis
  • use an appropriate scale for your axis - this should lead to a graph that uses more than 50% of the paper
  • when drawing a line or curve of best fit there must be a reasonable balance of plots either side of the line
  • a ruler should be used to draw a straight line of best fit
  • when the data produces a curve, the curve should be drawn smoothly free-hand