Definition
The correlation coefficient is usually defined by the formula
It is however easier to understand if written in terms of standardised versions of X and Y,
The correlation coefficient is a kind of average of the products of the z-scores.
How does r relate to the shape of a scatterplot?
The following properties of r explain in general terms how its value is related to the strength of a relationship in any particular scatterplot.
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−1 ≤ r ≤ +1 |