Question

If $ \Sigma x=15,\Sigma y=40,\Sigma xy=110 $ and $ n=5, $ then the value of cov $ (x,y) $ is

• A. $ -2 $
• B. 2
• C. 22
• D. None of these

Answer 1

Answer: (A)

Given, $ \Sigma x=15,\text{ }\Sigma y=40,\text{ }\Sigma xy=110,\text{ }n=5 $
$ \overline{X}=\frac{1}{n}\Sigma x=\frac{1}{5}\times 15=3 $
$ \overline{Y}=\frac{1}{n}\Sigma y $ $ =\frac{1}{5}\times 40=8 $
$ \operatorname{cov}(x,y)=\frac{1}{n}\Sigma xy-\overline{X}\overline{Y} $
$ =\frac{1}{5}\times 110-3\times 8 $
$ =22-24=-2 $