Calculate the mean and standard deviation for the set of numbers
{11,16, 20,17}
Mean = [ 11 + 16 + 20 + 17 ] / 4 = [ 64] / 4 =16
Variance = [ (11-16)^2 + (16 - 16)^2 + (20 - 16)^2 + (17-16)^2 ] / 4 =
[ 25 + 0 + 16 + 1 ] / 4 = [ 42 / 4] = [21 / 2 ] = 10.5
Standard deviation = √Variance = √10.5 ≈ 3.24 [assuming a populaton]
If this is a sample the Variance is [42 / (4 -1) ] = [42 / 3 ] = 14
And the Standard Deviation = √14 ≈ 3.74