The indicator adjusted uses to be far from value

A low value of  indicates a poor relation between X and Y or a non-linear relation

A high value of may indicate a good linear relation between X and Y

The indicator takes values between 0 and 1

In practise it is used the indicator adjusted , which is the value  ajusted to the degrees of freedom. It is slightly lower than

The indicator  takes values beween -1 and 1

A low value of may indicate a good linear relation between X and Y

A high value of  indicates a poor relation between X and Y or a non-linear relation