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# In a bivariate data $\Sigma x = 30\: \: \Sigma y = 400 \: \: \Sigma x^2=196 \: \: \Sigma xy = 850 \: \: n=10$  Find the regression coefficient of $y$ and $x$

$\begin {array} {1 1} (A)\;3.2 & \quad (B)\;3.3 \\ (C)\;-3.3 & \quad (D)\;1.3 \end {array}$

$b_{yx} = \large\frac{\Sigma xy - \large\frac{1}{n} \Sigma x. \Sigma y}{\Sigma x^2-\large\frac{1}{n} ( \Sigma x)^2}$
$= \large\frac{850- \large\frac{30 \times 400}{10}}{196- \large\frac{(30)^2}{10}}$
$= \Large\frac{850- \Large\frac{1200\not{0}}{1\not{0}}}{196- \Large\frac{90\not{0}}{1\not{0}}}$
$= \large\frac{850-1200}{196-90} = \large\frac{-350}{106}$
$= -3.3$
Ans : (C)