A researcher is carrying out a study of the effectiveness of two different skin creams in combination with two different retinol treatments (80% retinol and 30% retinol) for the treatment of a certain skin disease. He has 240 women and plans to divide them into 2 groups of 120 subjects each, according to how severe their skin condition is; the 120 most severe cases are the first group, the remaining moderate cases will be the second group. The members of each group are then randomly assigned to one of the treatment combinations. The women were unaware which skin cream they were using. Draw a diagram to represent this experiment. (Identify the subjects, the response variable, the treatments (including the # of treatments), where randomization occurs, and any factors that have already been controlled for) Was "Blinding" used in this experiment? Single or Double or neither? What other factors should be controlled for that might affect the response variable? Is there a placebo? Why do you think they did not have a control group in this experiment?