The sum of the squares deviations for 10 observations for 10 observations taken from their mean 50 is 250. The coefficient of variation is

A batsman scores runs in 10 innings as 38, 70, 48, 34, 42, 55, 63, 46, 54 and 44. The mean deviation about mean is

The mean deviation of the numbers 3, 4, 5, 6, 7 from the mean is

Let x₁, x₂, ……x_n be values taken by a variable X and y₁, y₂, …….y_n be the values taken by a variable Y such that y_i = ax_i + b, i = 1,2, …….,, n. Then,

If the standard deviation of a variable X is σ, then the standard deviation of the variable is