Final answer:
A randomized block design involves grouping similar subjects together to decrease variability and increase the efficiency of the study. In this case, there are four blocks of three homogeneous subjects.
Step-by-step explanation:
In a randomized block design, blocks are used to group similar subjects together to decrease the impact of variability. The treatments are then randomly assigned within each block, ensuring that each treatment is represented in each block. The purpose of this design is to control for potential confounding variables and increase the efficiency of the study.
In this case, there are four blocks, and each block consists of three homogeneous subjects. This means that within each block, the subjects are similar or have similar characteristics. By using a randomized block design, the mean responses for the three treatments can be compared more accurately.