8 The equations of the regression lines for a random sample of 25 pairs of data \(( x , y )\) from a bivariate population are
$$\begin{array} { c c }
y \text { on } x : & y = 1.28 - 0.425 x ,
x \text { on } y : & x = 1.05 - 0.516 y .
\end{array}$$
- Find the sample means, \(\bar { x }\) and \(\bar { y }\).
- Find the product moment correlation coefficient for the sample.
- Test at the \(5 \%\) significance level whether the population correlation coefficient differs from zero.