Calculates the sample standard deviation of the input values. Use if the values encompass a sample of a population of data from which to generalize about the population. $stdDevSamp ignores non-numeric values.
5.0
https://www.mongodb.com/docs/manual/reference/operator/aggregation/stdDevSamp/#mongodb-expression-exp.-stdDevSamp
Calculates the sample standard deviation of the input values. Use if the values encompass a sample of a population of data from which to generalize about the population. $stdDevSamp ignores non-numeric values.