6.8 Features of r

• Independent of origin and scale
• $-1 \le r \le 1$
• $r = \sqrt{b_{yx} \cdot b_{xy}}$ (Concerning GM of regression coeff)
• $\frac{b_{yx}+b_{xy}}{2} \ge r$ (About AM)
• $r = 0 \rightarrow$ no linear relationship