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.

def confidence_level(self):
        """
        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.
        """
        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"