# GCSE Maths Unit 1 - Scatterplot Graphs Guide

##### February 10, 2016

**GSCE Maths: Scatterplot Graphs**

A scatterplot graph has a positive correlation if the results are approximately in a straight line with a positive slope (i.e. as one rises, the other rises too). It has a negative correlation if the results are approximately in a straight line with a negative slope (i.e. as one rises the other falls). If the points on a scatterplot are not aligned with each other, no correlation exists.

If a correlation exists then a ‘line of best fit’ can be drawn, this is a line that best aligns the points – i.e. any points not on the line should be evenly distributed on either side of the line.

**Sample question**

Each day a taxi driver records the distance he travels and the amount of fuel his car uses.

Distance (km) | 87 | 122 | 97 | 90 | 105 | 100 | 135 | 116 |

Fuel (litres) | 8.3 | 13.0 | 9.5 | 9.4 | 11.2 | 9.9 | 14.0 | 12.0 |

i) Complete the scatter graph and draw a line of best fit.

ii) Use your line of best fit to predict the fuel used to travel 110 km.

**Solution**

i) The scatterplot shows a positive correlation between distance travelled and fuel used; so a line of best fit can be drawn. (i.e. the solid blue solid line)

ii) From the scatterplot, it can be seen that travelling 110km corresponds to a fuel use of approximately 11.3 litres.

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