We compare different permutation tests and some parametric counterparts that
are applicable to unbalanced designs in two by two designs. First the different
approaches are shortly summarized. Then we investigate the behavior of the
tests in a simulation study. A special focus is on the behavior of the tests
under heteroscedastic variances.Comment: 20 pages, 9 figures, Working Paper of the Department of Management
And Enigineering of the University of Padov