A block design is referred to as the randomized block design, which is to reduce variability among gender groups. This design is both random and controlled. For instance, say that we have sample of new drug in the market for those who are suffering from a disease. The experimenters will use take a random number of subjects with the disease, and equally assign them to either the real drug or the placebo. Subjects are told that they will be taking a drug that helps them with the disease, but experimentally they have no idea whether if they are taking the drug or the placebo.