# Calculate standard deviaton based on population/sample
import numpy as np
values = [1,5,4,3,3,4]
# as default, std() calculates basesd on a population
# by specifying ddof=1, it calculates based on the sample
np.std(values) # ==1.247219128924647
np.std(values ,ddof=1) # ==1.3662601021279464