You are a researcher studying the health affects of a daily multi-vitamin. You first categorize your study population into age groups: 5-10, 10-25, 25-35, 35-50, and 50-70. You then randomly assign a multi-vitamin or a placebo to a certain number of participants in each group. What is this experimental design process called? randomized group design Press 1 randomized block design Press 2 O random control design Press 3 random confounding design Press 4