@staticmethod
def msd_ratio_(msd_ea, n1, n2):
    """
        Ratio of the ensemble averaged mean squared displacements.

        .. math::
            \\langle r^2 \\rangle_{n_1, n_2} = \\frac{\\langle r^2 \\rangle_{n_1 }}
            {\\langle r^2 \\rangle_{n_2 }} - \\frac{n_1}{n_2}

        with
        
        .. math::
            n_1 < n_2
            
        :return msd_ratio:
        """
    msd_ratio = msd_ea[n1] / msd_ea[n2] - n1 / n2
    return msd_ratio
