Researchers are interested in testing whether a video game that is designed to increase brain activity actually works. To test this, they plan to randomly assign subjects to either the treatment group (spend 15 minutes per day playing the game) or a control group (spend 15 minutes per day surfing the Web). At the end of the study, the researchers will administer a test of "brain teasers" to see which group has the greater mental agility. 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 in a box. The tickets are labeled with the age groups. When an age group is selected, everyone in that age group will be assigned to the treatment group. They will select two age groups to go to treatment, and two to go to control. Is this an appropriate use of blocking? If so, explain why. If not, describe a better blocking plan.
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