Three sales training seminars are tested for effectiveness; size of organization is a blocking factor. A total of four organizations were chosen, one from each of four size groups. At each organization, 15 salespeople were randomly assigned to 3 groups of size 5. Each group was randonly assigned to one of the three seminars. After 1 month, the relative improvement in each person's monthly sales was measured.
What is the name of this design? What is the experimental unit and what is the observational unit? Would it be proper to test for an effect due to organization size?