Question

It’s either D or E; please help

Thirty overweight males agree to participate in a study of the effectiveness of three weight-loss treatments: X, Y, and Z. The researcher calculates the
body fat composition of each subject. The response variable is the reduction in body fat after six weeks of treatment. Previous studies have shown the
effects of a diet may vary based on a subject's initial body fat composition. How should the subjects be blocked? Explain.

They should be blocked alphabetically so the subjects are as different as possible.

They should be blocked by age because weight loss is more difficult to achieve as you get older.

They should be blocked by height because weight loss is easier to achieve for taller people.

They should be blocked by body fat composition so the subjects are as similar as possible.

Blocking should not be used in this experiment.

Answer 1

They should be blocked by body fat composition so the subjects are as similar as possible.

Explanation:

It's D .

Blocking here means how should the subjects be arranged in terms of body fat or weight.

Option A is wrong because alphabetically controlling body fat would not get desired results.

Option B is wrong because different age groups would yield different results.

Option C is wrong also because weight loss is not dependent on taller people.

Option D is correct because controlling body fat would yield best possible results in ascending or descending order

Option E is incorrect because arranging data in ascending or descending order would simplify the researches experiments.