Strength of associations

Textbooks provide plots with dots showing:

  • no association
  • moderate association
  • strong association

for both positive and negative associations.

They will look similar to the diagrams below.

Association is measured with the correlation coefficient, where no association relates to a correlation of 0, a very strong positive association has a correlation near +1 and a very strong negative association has a correlation near –1.


Seven scatter plots show the range of associations from a correlation of +1 through 0 to –1.

Strength of associations.

Examples of scatter plots and an activity can be be found in Is There an Association? and Judging Associations.

Curriculum links

Year 10: Use scatter plots to investigate and comment on relationships between two numerical variables