The formula for calculating standard deviation of a sample is expressed as
Standard deviation = √Σ(x - mean)^2/(n - 1)
where
n = the number of samples = 5
Mean = (17 + 20 + 44 + 39 + 40)/5
Mean = 32
Σ(x - mean)^2 = (17 - 32)^2 + (20 - 32)^2 + (44 - 32)^2 + (39 - 32)^2 + (40 - 32)^2 = 626
n - 1 = 5 - 1 = 4
Standard deviation = √(626/4)
Standard deviation = 12.51