def __getStandardDeviation(self):
      """Determine the measure of the dispersion of the data set based on the
      variance.
      """

      from math import sqrt     # Mathematical functions.

      # Take the square root of the variance.
      self.stddev = sqrt(self.variance)
Determine the measure of the dispersion of the data set based on the
      variance.
      
recipes/Python/409413_Pythonbased_descriptive_statistical/recipe-409413.py