To group the bars, use something like this:
qual = rand(57);
qual_jong = rand(29);
qual_oud = rand(29);
d = [qual(57,3:14); qual_jong(29,3:14); qual_oud(29,3:14)];
figure
bar(d); % or use d' depending on the desired grouping
The 'grouped' modifier has no effect in your code because the data in each bar function are just a vector.
