Suppose you want to compare the effectiveness of the flu vaccine in preventing the flu using one of two different forms: nasal spray vs. injection. Suppose you have 60 subjects available of different ages, and you suspect that age might have an effect on the outcome. Assume there are 20 children aged 2 to 15, 20 people aged 16 to 30, and 20 people aged 31 to 49.
a. Identify the treatment variable and the response variable.
b. Describe a simple randomized design (no blocking) to test the whether the injection or the nasal spray is more effective. Explain in detail how to assign people to treatment groups.
c. Describe a blocked design (blocking by age) to test whether the injection or the nasal spray is more effective. Explain in detail how you will assign people to treatment groups.
d. What advantage does the blocked design have?