
Coding method
One of the formulae for coefficient of correlation is given as
$\displaystyle r=\frac{n\Sigma XY(\Sigma X)(\Sigma Y)}{\sqrt{[N\Sigma X^2(\Sigma X)^2][N\Sigma Y^2(\Sigma Y)^2]}}$ eq(1)
For coding method of bivariate frequency table, it's given as
$\displaystyle r=\frac{n\Sigma fu_Xu_Y(\Sigma f_Xu_X)(\Sigma f_Yu_Y)}{\sqrt{[N\Sigma f_Xu_X^2(\Sigma f_Xu_X)^2][N\Sigma f_Yu_Y^2(\Sigma f_Yu_Y)^2]}}$ eq(2)
I need to derive eq(2).
I began by$\displaystyle \overline X=A+(\frac{\Sigma f_Xu_X}{n})c$, where c is class interval, and $\displaystyle u=0, \pm1, \pm 2, ...$ and got
$\displaystyle \Sigma X = NA_x+c\Sigma f_xu_x $, similarly $\displaystyle \Sigma Y = NA_y+c\Sigma f_yu_y$, but I do not know how to get to $\displaystyle \Sigma XY$
I have a hunch that I need to make a table, but how?
Can anyone point me in the right direction?

I solved it.
Thread closed.