“…However, the 20%-trimmed t-test protects at most against a single outlier in case of the window widths considered here, and t-test on ranks had little robustness against outliers at all. Among tests based on local variabilities such as those based on quasi-ranges (Restrepo and Bovik, 1988, Sun and Venetsanopoulos, 1988, Kundu and Wu, 1989, Lee and Tantaratana, 1990, Sun, Gabbouj and Neuvo, 1994, only the empirical variance gave good power, but for the price of a strong increase of the test size already in case of a single outlier or a change of the variance. Similar problems were observed with linear hybrid edge detectors (Neuvo, Heinonen and Defee, 1987).…”