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Website
Wolfram Research

Wolfram Math World: Correlation Coefficient

For Students 9th - 10th Standards
MathWorld offers a technical, yet informative, explanation of the correlation coefficient for bivariate normal distribution.
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Handout
University of Glasgow

Steps: Pearson's Product Moment Correlation Coefficient

For Students 9th - 10th Standards
Overview of Pearson's Product Moment Correlation Coefficient, which is just one example of a correlation coefficient.