1. Scatter Diagrams Isabel Smith

2. Why do we use scatter diagrams?  We use scatter diagrams to see whether two sets of data are linked, e.g. height and shoe size  Using a scatter diagram makes the links, if there are any, clearer to see

3. Example Scatter Diagram

4. The Line of Best Fit  The line of best fit is the line we draw on our graph to show the general trend of the points  At GCSE level, the line is generally drawn by sight and is not calculated  You should try to get the same amount of points on both sides of the line

5. Example Scatter Diagram with the Line of Best Fit

6. Correlation – Strong or Weak?  Correlation is the link between two sets of data  Correlation can be strong or weak and positive or negative  Strong correlation means there is a strong link between the two sets of data, so the points are in a straighter line and are close to the line of best fit  We say the correlation is weak if the dots are more spread out, but still have a general trend  If the dots are completely random, we say there is no correlation

7. Correlation – Positive or Negative?  In the example scatter diagram, the higher the maths score, the higher the physics score was as well  We describe this correlation as positive as the line of best fit is positive, i.e. the diagonal goes from the bottom left to top right  If it was the other way around and the higher the maths score, the lower the physics score, the correlation would be negative

8. Example Scatter Diagram 2 This graph has weak negative correlation

9. Example Scatter Diagram 3 This graph has no correlation