Researchers are interested in testing whether a video game increases brain activity. They plan to randomly assign subjects to either the treatment group (15 minutes per day playing the game) or a control group (15 minutes per day surfing the web). Because they suspect that age might affect the outcome, the researchers will create blocks of ages:
18-25,
26-35,
36-45,
and
46–55.
To randomly assign subjects to treatment or control, they will place four tickets, labelled with the age groups, in a box. When an age group is selected, everyone in that age group will be assigned to the treatment group. They will select two tickets, and those age groups will be assigned to the treatment group. The other two age groups will be assigned to the control group. Is this an appropriate use of blocking? If so, explain why. If not, describe a better blocking plan.
A.
This is not an appropriate use. They should assign each patient within the first block (age group) a number and put all the numbers in a box. They should pick out half of the numbers and assign these patients to the treatment group. Then repeat for the other three blocks.
B.
This is an appropriate use because the researchers identified a variable that they thought might affect the outcome, age. Since the ages of the patients cannot be controlled, they grouped patients of similar age together to create the blocks.
C.
This is not an appropriate use. They should randomly assign half of the patients to the treatment group and half to the control group. Then they should record how many of each age group are in the treatment group and how many are in the control group.
D.
This is not an appropriate use. They should assign each patient in each age group with a 0 or a 1. Then they should put these numbers in a box and pick out one of them. The patients with that number should be assigned to the treatment group. Then repeat for the other three blocks.
Option A) is the most appropriate.
Since the groups (blocks) have been created on the basis of age, half od the persons in each age group should be assigned to treatment group and the other half should be in control group. The same thing should happen for each of the other three blocks. In this case, both the treatment and the control groups will have the same number of persons from different age groups.
Option B is definitely not correct as it is not making any use of the blocking at age.
Option C is also mot correct as it is first assigning the people to treatment and control group and then listing their age. In this case, it might happen that people of same age group are in treatment only or otherwise.
Option D is also not the most appropriate thing to do as it is not dividing the people in the same age group as half among the treatment and control group
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