text: from __future__ import division
  from __future__ import absolute_import
  
  
  def test_variance():
      data = [4, 7, 13, 16]
  
      def naive_var(data):
          n = len(data)
          return ((
              sum(di**2 for di in data)
              - sum(data)**2/n)
              / (n-1))
  
      from pytools import variance
      orig_variance = variance(data, entire_pop=False)
  
      assert abs(naive_var(data) - orig_variance) < 1e-15
  
      data = [1e9 + x for x in data]
      assert abs(variance(data, entire_pop=False) - orig_variance) < 1e-15
  