If the mean and variance of the following dat | vedclass

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Question

$	ext { Mean }=\frac{6+10+7+13+a+12+b+12}{8}=9$

$60+a+b=72$

$a+b=12$

$	ext { veriance }=\frac{\sum x_{i}^{2}}{n}-\left(\frac{\sum x_{i}}{n}

Vedclass · Accepted Answer

$16$

Vedclass · Answer

$	ext { Mean }=\frac{6+10+7+13+a+12+b+12}{8}=9$

$60+a+b=72$

$a+b=12$

$	ext { veriance }=\frac{\sum x_{i}^{2}}{n}-\left(\frac{\sum x_{i}}{n}ight)=\frac{37}{4}$

$\sum x_{i}^{2}=6^{2}+10^{2}+7^{2}+13^{2}+a^{2}+b^{2}+12^{2}+12^{2}$

$=a^{2}+b^{2}+642$

$\frac{a^{2}+b^{2}+642}{8}-(9)^{2}=\frac{37}{4}$

$\frac{a^{2}+b^{2}}{8}+\frac{321}{4}-81=\frac{37}{4}$

$\frac{a^{2}+b^{2}}{8}=81+\frac{37}{4}-\frac{321}{4}$

$\frac{a^{2}+b^{2}}{8}=81-71$

$	herefore a^{2}+b^{2}=80$

From $(1)$ $a^{2}+b^{2}+2 a b=144$

$80+2 a b=144 	herefore 2 a b=64$

$(a-b)^{2}=a^{2}+b^{2}-2 a b=80-64=16$

$x_i$	$2$	$4$	$6$	$8$	$10$	$12$	$14$	$16$
$f_i$	$4$	$4$	$\alpha$	$15$	$8$	$\beta$	$4$	$5$

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