Varsity Tutors
Varsity Tutors: Hotmath: Practice Problems: Correlation and Lines of Best Fit
Twenty problems present a variety of practice determining correlation based on data in a scatter plot and using lines of best fit with given data. They are given with each step to the solution cleverly revealed one at a time. You can...
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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.