Additional Principles of Experimental Design — Quiz
Question 7 • Statistics and Probability
A doctor wants to determine if a new medication for cholesterol is more effective than the previous medication. The doctor informs patients of a new medication and asks if they want to participate; 30 patients who are currently taking medication for cholesterol volunteer to be part of the study. She uses random assignment of the 30 patients to two treatment groups: one that uses the new medication, and one that uses the original medication. Which of the following describes the benefit of random assignment?
Answer
A
The variability between the subjects would be evenly distributed between the two groups, so any observed differences in the cholesterol level between the two groups would be guaranteed to be due to the new medication.
B
The variability between the medications would be evenly distributed between the two groups, so any observed differences in the cholesterol level between the two groups would be guaranteed to be due to the subjects.
C
The variability between the subjects would be evenly distributed between the two groups, so any observed differences in the cholesterol level between the two groups would more likely be due to the new medication.
D
The variability between the medications would be evenly distributed between the two groups, so any observed differences in the cholesterol level between the two groups would more likely be due to the subjects.
Explanation
Random assignment tends to distribute differences among the patients—such as their starting cholesterol levels—across both groups. This makes the groups more comparable, so a difference in cholesterol levels is more likely to reflect the medication rather than differences between the patients. It does not guarantee that the groups will be identical or that every observed difference is caused by the new medication.
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