Bar charts

Part of MathsRepresenting data

Key points

An image of a dual bar chart.
Bar graphs are used to show sets of data in more specific categories.

  • A bar chart is a type of graph used to represent a or set of data. It uses different height rectangles, or bars, to represent the of each category.

  • It can be used to make comparisons between the categories in a set of data.

  • The frequency is usually represented on the . The labelling on the depends on what data the bar chart is representing.

  • A bar chart should have gaps between the bars.

An image of a dual bar chart.
Bar graphs are used to show sets of data in more specific categories.
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Creating a bar chart

  • To create a bar chart data is required. The data often comes in the form of a table.

  • To create a bar chart:

    1. Look for the largest frequency in your table.
    2. Draw a on your square paper or graph paper.
    3. Choose an appropriate scale for this axis and label your axis up to the largest frequency.
    4. Look at how many categories are needed for the horizontal axis.
    5. Draw and label the , remembering to leave spaces for the gaps between the bars.
    6. Draw each bar the correct height, based on the frequencies.
    7. Check you have labelled each axis correctly and give your bar chart a title.

Examples

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  1. Example one. An image of a table. The table has two rows and five columns. The first row is labelled, season, and is populated with, spring, summer, autumn, and winter. The second row is labelled, frequency, and is populated with the numbers, ten, twelve, three, and seven. The cells for the labels are coloured purple.

    32 students were asked which season was their favourite. The table shows the results. Construct a bar chart that represents these results.

Questions

This bar chart shows student’s favourite colour.

How many students were asked what their favourite colour was?

An image of a bar chart. A vertical axis has been drawn to the left. The axis has been labelled with numbers. The values are increasing in units of two from zero to twelve. The axis has also been labelled, frequency. The horizontal axis has been labelled, blue, red, green, purple, and other, such that each bar has a width of one square. Between each label is a gap of width equalling one square. Written beneath the labels: colour. A bar of height, six, has been drawn above the label blue. A bar of height, nine, has been drawn above the label red. A bar of height, two, has been drawn above the label green. A bar of height, three, has been drawn above the label purple. A bar of height, six, has been drawn above the label others. Written above: A bar chart to show student’s favourite colours. The colour of each bar corresponds to the colour it represents. The others bar is coloured grey.

This compound bar chart shows the outcome of fixtures for four football teams for a season.

What percentage of games did Torquay United draw?

An image of a compound bar chart. A vertical axis has been drawn to the left. The axis has been labelled with numbers. The values are increasing in units of ten from zero to one hundred. The axis has also been labelled, percentage. The horizontal axis has been labelled with the names of four teams, Wrexham, Notts County, York City, and Torquay United, such that each bar has a width of three squares. Between each label is a gap of width equalling one square. Written beneath the labels: teams. Each bar above a team comprises three sections, coloured, green, red, and blue. For Wrexham, the green bar has a frequency of sixty percent, the red bar goes from sixty to seventy percent and the blue bar goes from seventy to one hundred percent. For Notts County, the green bar has a frequency of fifty percent, the red bar goes from fifty to eighty percent and the blue bar goes from eighty to one hundred percent. For York City, the green bar has a frequency of thirty percent, the red bar goes from thirty to sixty percent and the blue bar goes from sixty to one hundred percent. For Torquay United, the green bar has a frequency of thirty percent, the red bar goes from thirty to eighty percent and the blue bar goes from eighty to one hundred percent. Written above: A compound bar chart to show football results. Written right: a key. Green equals win. Red equals lose. Blue equals draw.

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Practise working out bar charts

Practise working out bar charts with this quiz. You may need a pen and paper to help you with your answers.

Quiz

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Real-life maths

A businessman drawing a curved vertical line with a pen over the bars of a graph rising from the keyboard of a laptop – the bars are green and ascending in high and by twenty percentage for each one starting zero percent up to one-hundred percent. The same percentages are also listed to the right of the graph. Written below the them: Emissions.
Scientists can use bar graphs to sort and analyse data about the environment and climate.

A may use climate graphs to study changes in weather patterns in regions of the world. One type of climate graph shows precipitation or rainfall. This takes the form of a bar chart with the rainfall for each month being represent as a bar. The height of the bar indicates the quantity of a rainfall during that month.

A businessman drawing a curved vertical line with a pen over the bars of a graph rising from the keyboard of a laptop – the bars are green and ascending in high and by twenty percentage for each one starting zero percent up to one-hundred percent. The same percentages are also listed to the right of the graph. Written below the them: Emissions.
Scientists can use bar graphs to sort and analyse data about the environment and climate.
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Game - Divided Islands

Use your maths skills to help the islanders of Ichi build bridges and bring light back to the islands in this free game from BBC Bitesize.

Divided Islands
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