def corrections(mean_onbit_density):
    """Calculate corrections

    See :func:`similarity` for explanation of corrections.

    Args:
        mean_onbit_density (float): Mean on bit density

    Returns:
        float: S\ :sub:`T` correction, S\ :sub:`T0` correction
    """
    p0 = mean_onbit_density
    corr_st = (2 - p0) / 3
    corr_sto = (1 + p0) / 3
    return corr_st, corr_sto