Scatter Diagrams, Correlation and Lines-of-Best-Fit

Statistics - learn about scatter diagrams (scattergrams), types of correlation, finding the mean point, and drawing lines-of-best fit

Author and programmer: Ron Barrow

UK Years 7-11, KS3, KS4, GCSE Mathematics, Grades C - A*, Probability and Data handling


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How to Use this Applet

On the graph at the left of the screen, you can plot points by clicking the mouse at those points. In this way you can build up a scatter diagram. You can click up to 100 points.
Then you can use the green line at the top of the page to try to find a line-of-best-fit for the graph. Just click-and-drag the red points at the ends of the line to move the line to where you think it should be. You can turn this feature off by clicking the "your line-of-best-fit" checkbox at the bottom.
Clicking "correlation type" will show you if your points show any kind of correlation, and describe the type of that correlation.

At any time you can click "mean point", which will show the Mean Point of the two sets of data. Doing this before you draw your line-of-best-fit will help to make it more accurate, as your line should pass through the Mean Point.
Checking the box marked "computer's line-of-best-fit" will draw a calculated, accurate line-of-best-fit (regression line), so that you can see how well you did. The equations of the two lines are shown on the right of the page.
Start clicking away! Practise drawing lines-of-best-fit. Enjoy and learn!