Anything non linear or multivariate: http://en.wikipedia.org/wiki/Correlation_and_dependence http://en.wikipedia.org/wiki/Correlation_and_dependence Ie unempl

Anything non linear or multivariate: http://en.wikipedia.org/wiki/Correlation_and_dependence http://en.wikipedia.org/wiki/Correlation_and_dependence Ie unemployment is not correlated with age since both young and old people tend to be unemployed...it is a non-linear relationship.