• Correlation and regression are both techniques that tell us the degree of linear association between two variables. Correlation tells us the strength and direction of the association. Regression allows us to predict one value from another.
  
  
• We can have three types of correlations: (1) positive correlation, (2) negative correlation, and (3) zero correlation.
  
  
• Correlations can be thought of as an index of relative rank. If we are high (above the mean) on one variable, are we also high (above the mean) on a second variable?
  
  
• Correlations are standardized; they can only range in value between –1.0 and +1.0.
  
  
• The coefficient of determination (r²) tells us the percent variance in Y (our dependent variable) that is explained by X (our independent variable).
  
  
• The regression line always has the form Y = bX + a.

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