Correlation Coefficient

A correlation coefficient is a number between -1 and 1 which measures the degree to which two variables are linearly related.

If the two variables relate linearly with a positive slope, the correlation coefficient is unity (ie. 1) and is said to be positive. Conversely, if they relate linearly but with a negative slope, the correlation coefficient is minus unity (ie. –1) and is said to be negative.

A correlation coefficient of 0 means that the two variables have no linear relation.

There are a number of different correlation coefficients that might be appropriate depending on the types of variable being studied.