# Scatter diagrams - line of best fit

The 'line of best fit' goes roughly through the middle of all the scatter points on a graph. The closer the points are to the line of best fit, the stronger the correlation is.

### Example

Ten pupils in a school study French and German at GCSE. Their marks in recent tests are recorded in the table below:

BenSarahSunilTomPeteHenrySiobhanAndrewJoGita
Mark in French
Mark in German

Draw a scatter diagram to represent these marks. As Pete was absent on the day of the German test you do not have enough information to mark his score.

Looking at this scatter diagram, there is strong positive correlation between the marks in French and the marks in German - so you can draw a line of best fit to show that trend.

Pete scored in French, so using the line of best fit, you can estimate that his mark in German would have been approximately .

• A line of best fit can only be drawn if there is strong positive or negative correlation.
• The line of best fit does not have to go through the origin.
• The line of best fit shows the trend, but it is only approximate and any readings taken from it will be estimations.
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