def NIST_SU(results):
    """Number of segmentation errors (missed segments and
    false alarm segments)
    over number of reference segments.
    """
    assert len(results) == 3
    TPs = results[0]
    FPs = results[1]
    FNs = results[2]
    if (FNs + FPs) == 0:
        return 0.0
    return ((FNs + FPs)/(TPs + FNs)) * 100