Question

select all the correct answers.

a group of scientists is conducting an experiment on the effects of media on children. they randomly select 100 children and randomly assign each child to one of four treatment groups. each treatment group has a specific amount of screen time during a one-week time frame. the first group has no screen time, the second group has two hours of screen time, the third group has four hours of screen time, and the fourth group has six hours of screen time.

after the first week, the scientists conduct the same experiment, with the same subject groups, for three more weeks so that each group experiences each of the four treatments.

which statements about this study are true?

this study uses blocking.
this study uses blinding.
this study uses a control group.
this study uses a repeated measures design.
this study uses random sampling.

Explanation:

Analyze the study design and treatments

• The study randomly selects 100 children (random sampling).
• The first group has no screen time, which serves as a control group.
• Over four weeks, each group experiences each of the four treatments, which defines a repeated measures (or crossover) design.

Evaluate the given statements

• "This study uses blocking": False. The subjects are not divided into blocks based on an pre-existing characteristic before assignment.
• "This study uses blinding": False. There is no mention of children or researchers being unaware of the treatments.
• "This study uses a control group": True. The group with "no screen time" is a control group.
• "This study uses a repeated measures design": True. Each subject group experiences all four treatments sequentially over four weeks.
• "This study uses random sampling": True. The text states "They randomly select 100 children".

Answer:

• This study uses blocking
• This study uses blinding
• This study uses a control group (Correct answer)
• This study uses a repeated measures design (Correct answer)
• This study uses random sampling (Correct answer)