def empirical_power(n_tp, n_at):
    """Computer empirical power.

    Input arguments:
    ================
    n_tp : int
        The observed number of true positives.

    n_at : int
        The number of hypotheses for which the alternative is true.

    Output arguments:
    =================
    epwr : float
        Empirical power.
    """

    """Compute the empirical power. Check that the result is in [0, 1]."""
    pwr = float(n_tp) / float(n_at)
    if ((pwr > 1) | (pwr < 0)):
        raise Exception('Invalid input parameters!')

    return pwr