The mean and variance of the data $$4,5,6,6,7,8, x, y$$, where $$x< y$$ are 6 and $$\frac{9}{4}$$, respectively. Then, $$x^2-2 y$$ is equal to

The mean of five observations is 4 and their variance is 5.2. If three of these observations are 1, 2 and 6, then the other two are

For a random variable X, E(X) = 3 and E(X²) = 11. The variable of X is :

The sum of 10 items is 12 and the sum of their squares is 18, then the standard deviation will be