I have collected data from three groups (with different sizes of n). This was done with a test instrument consisting of 9 items, each binary coded (1 = right, 0 = wrong). The results are not equally distributed.
I now want to show that there is a signifikant difference between the three groups for the total score of the test (min = 0, max = 9), but also for the single items.
I did a Kruskal-Wallis for the total score and the results were promising. Now I am unsure if I can use the same test for the individual items because they only have binary values (0 and 1).
So, is it useful to do a Kruskal-Wallis for binary data? Is there any other test I could use?