Quia
Ixl Learning: Correlation
Brush up on your math skills relating to correlation then try some practice problems to test your understanding.
Other
Correlation Coefficients
This page provides a good discussion of correlation coefficients (r,) which indicate the "strength of the linear association between variables." Includes formulas and scatter plots. Some prior knowledge of statistics might be helpful.
University of Glasgow
Steps: Pearson's Product Moment Correlation Coefficient
Overview of Pearson's Product Moment Correlation Coefficient, which is just one example of a correlation coefficient.