code: def confidence_level(self):
          
          z = self.z_score
          if isinstance(z, string_types):
              return z
  
          z = abs(round(z, 3))
  
          if z == 0.0:
              return "No Change"
          elif z < 1.65:
              return "No Confidence"
          elif z < 2.33:
              return "95% Confidence"
          elif z < 3.08:
              return "99% Confidence"
          return "99.9% Confidence"
docs: Based on the variant's Z-Score, returns a human-readable string that
          describes the confidence with which we can say the results are
          statistically significant.