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Pie charts

Pie charts show percentages as a circle, divided into segments. A pie chart could be used to show how students travel to school. Each piece of data is shown as a proportion of 360, because there are 360 degrees in a circle. If 25 out of 100 students travel to school by car, the angle is worked out using the calculation: (25 ÷ 100) × 360 = 90 degrees.

Scatter graphs

Scatter graphs show relationships between two sets of data. Points are located using the x and y-axis. Sometimes these points are arranged in a pattern. A scatter graph could be used to show how literacy is related to GDP.

A line of best fit helps to show correlations, or patterns within the data. The line of best fit runs through the middle of a collection of points on the graph, ideally with an equal number of points on either side of the line.

• A strong correlation is when the points are very close to the line of best fit.
• A weak correlation is when the points are far away from the line of best fit.
• A positive correlation is when an increase in one factor is mirrored by an increase in another (the line of best fit goes from the bottom left to the top right).
• A negative correlation is when an increase in one factor is mirrored by a decrease in another (the line of best fit goes from the top left to the bottom right).

Proportional symbols, pictograms and cross sections

Proportional symbols can be added to maps or graphs to show information about different places. The graph below plots life expectancy against income for each country. It also shows population size. Each country is shown as a circle, where the size of the circle is proportional to the population of the country, ie the bigger the circle, the bigger the population of that country.

Pictograms are like bar charts, but they use small pictures or icons to show data instead of bars. Pictograms could be used to show the weather conditions experienced in a particular place over a period of time.

Cross sections are line graphs that show a sideways view of a landscape. They can show features such as hills and valleys, or depths, such as the depth of a river. Cross sections of hills use contour lines to determine the height of the land. Cross sections of river depths are drawn using negative numbers so that the line graph looks like depth, rather than height.

Radial/radar graphs

Radial/radar graphs are sometimes called rose charts. They have a central point from which data radiates outwards. This data can be plotted as points along a line, where all points are joined up to form a shape. It could also be plotted as segments along a line. Wind speed and direction is often shown as a radial graph. Radial graphs can show lots of different data and do not have to involve compass points.