A college professor conducts an experiment to determine if students perform better on exams when they study alone or in small groups. A total of 150 students taking an introduction to sociology course volunteer to participate in the study. Students are randomly assigned either to study alone for an upcoming exam or are assigned to a study group. The exam grades are then compared. Which of the following accurately describes the benefit of random assignment in the experiment?
Answer
A
Students of different abilities are more likely to be evenly distributed, so any differences observed in the exam grades are more likely to be a result of the treatment.
B
Students of different abilities are more likely to be evenly distributed, so any differences observed in the exam grades are guaranteed to be a result of the treatment.
C
Students of different abilities are less likely to be evenly distributed, so any differences observed in the exam grades may or may not be a result of the treatment.
D
There is no benefit of random assignment in the experiment.
Explanation
Random assignment tends to distribute students with different abilities and other characteristics similarly between the two groups. This helps make the study-alone and study-group groups comparable, so a difference in exam grades is more likely to be caused by the study method. It does not guarantee that the treatment caused the difference, because chance variation and other factors can still affect results.
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