# Pandas and NumPy Return Different Values for Standard Deviation. Why?

Pandas assumes that the data is a sample of the population and that the obtained result can be biased towards the sample.

Thus, to generate an unbiased estimate, it uses (n-1) as the dividing factor instead of n. In statistics, this is also known as Bessel's correction.

NumPy, however, does not make any such correction.

Find more info here: Bessel’s correction.

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