sqrt(Chi_Squared) statistic (see `mcc`, `phi`, or google 'Matthews Correlation Coefficient

def get_chi(self, scalar=None):
        """sqrt(Chi_Squared) statistic (see `mcc`, `phi`, or google 'Matthews Correlation Coefficient'"""
        phi = self.get_phi(scalar=scalar)
        return mcc_chi(phi, self._num_samples)