randomizing sub groups while keeping big loop sequential order
I want to design this experimental structure:
-- block sequence loop (repeated 8 times)
-- random sequence type 1 (1 out of 8)
-- random sequence type 2 (1 out of 8)
-- random sequence type 3 (1 out of 8)
-- random sequence type 4 (1 out of 8)
I would like to know how can a sequence be picked randomly in each type, but still keep the sequence of the big loop (type 1, and then 2, 3 and 4 in that order)?
And also, in total, I need to show all the sequences in the big loop in that order, without repeating on a sequence, so all 32 sequences will be shown, each in its group type, but they will be picked randomly from the pool. how can I be sure all 32 sequences will be shown once without repetition or emissions?
I hope I succeeded to explain myself well...
Thank you for your help!!