 Graph of a set of data points  Used to evaluate the correlation between two variables

 The line of best fit - a straight line that best represents the data on a scatter plot.  This line may pass through some of the points, none of the points, or all of the points.

 r measures the strength and direction of the relationship between 2 variables  -1≤ r ≤1  A correlation greater than 0.8 is generally described as strong, whereas a correlation less than 0.5 is generally described as weak.

 r is positive  As x increases, y also increases  If x and y have a strong positive linear correlation, r is close to 1

 r is negative  As x increases, y decreases  If x and y have a strong negative linear correlation, r is close to -1

 random, nonlinear relationship between the two variables  Points show no pattern  r is near zero

correlation coefficient, r = 1correlation coefficient, r = -1

Correlation does not prove causation!!!