Researchers conducted an experiment to compare the effects of a carbohydrate-restricted diet (low-carb diet) and a calorie- and fat-restricted diet (low-fat diet) on weight loss. The researchers are concerned that the effect of diet may depend on gender, so sex is treated as a blocking variable. There are 122 severely obese individuals available for the study, 52 of whom are men and 70 of whom are women.
Identify the most appropriate experiment design for the experiment.
A.
Randomly assign all subjects to two groups. Next, split each group into two sub-groups by sex. Next, assign one sub-group to low-carb diet and the other sub-group to the low-fat diet in both the groups. Compare weight loss within the groups.
B.
Use a coin to decide which subject receives which treatment. Divide subjects into two groups depending on which treatment they are receiving. Next, split each group into two sub-groups by sex. Compare weight loss within the groups.
C.
Split the subjects into two groups by sex. Create two sub-groups each in the two groups by random assignment. Next, within each group, assign one sub-group to low-carb diet and the other sub-group to the low-fat diet. Compare weight loss within the groups.
Answer: C.
Split the subjects into two groups by sex. Create two sub-groups each in the two groups by random assignment. Next, within each group, assign one sub-group to low-carb diet and the other sub-group to the low-fat diet. Compare weight loss within the groups.
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