Question

The mean of $40$ observations is $20$ and their standard deviation is $5.$ If the sum of the squares of the observations is $k$ , then the value of $\frac{k}{1000}$ is

Answer 1

$n=40$
$\bar{x}=20$
$\sigma =05$
$\left(\sigma \right)^{2}=\frac{\displaystyle \sum x_{i}^{2}}{40}-\left(\bar{x}\right)^{2}$
$25=\frac{\displaystyle \sum x_{i}^{2}}{40}-400\Rightarrow \displaystyle \sum x_{i}^{2}=17000$