def normalized_probs(p_mem, p_non, p_a):
    """
    Walker 2009 equation 11
    Parameters
    ----------
    p_mem: np.array
    p_non: np.array
    p_a: np.array

    Returns
    -------
    norm_probs: np.array
    """

    p_m = (p_mem*p_a)/(p_mem*p_a + p_non*(1.0 - p_a))
    return p_m